Artículos de revistas: "Il gene MEF"

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Marimón, José María, Adoración Valiente, María Ercibengoa, José M. García-Arenzana y Emilio Pérez-Trallero. "Erythromycin Resistance and Genetic Elements Carrying Macrolide Efflux Genes in Streptococcus agalactiae". Antimicrobial Agents and Chemotherapy 49, n.º 12 (diciembre de 2005): 5069–74. http://dx.doi.org/10.1128/aac.49.12.5069-5074.2005.

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ABSTRACT The macrolide resistance determinants and genetic elements carrying the mef(A) and mef(E) subclasses of the mef gene were studied with Streptococcus agalactiae isolated in 2003 and 2004 from 7,084 vaginorectal cultures performed to detect carrier pregnant women. The prevalence of carriage was 18% (1,276 isolates), and that of erythromycin resistance 11.0% (129 of the 1,171 isolates studied). erm(B), erm(A) subclass erm(TR), and the mef gene, either subclass mef(A) or mef(E), were found in 72 (55.8%), 41 (31.8%), and 12 (9.3%) erythromycin-resistant isolates, while 4 isolates had more than 1 erythromycin resistance gene. Of the 13 M-phenotype mef-containing erythromycin-resistant S. agalactiae isolates, 11 had the mef(E) subclass gene alone, one had both the mef(E) and the erm(TR) subclass genes, and one had the mef(A) subclass gene. mef(E) subclass genes were associated with the carrying element mega in 10 of the 12 mef(E)-containing strains, while the single mef(A) subclass gene found was associated with the genetic element Tn1207.3. The nonconjugative nature of the mega element and the clonal diversity of mef(E)-containing strains determined by pulsed-field gel electrophoresis suggest that transformation is the main mechanism through which this resistance gene is acquired.

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Mingoia, Marina, Manuela Vecchi, Ileana Cochetti, Emily Tili, Luca A. Vitali, Aldo Manzin, Pietro E. Varaldo y Maria Pia Montanari. "Composite Structure of Streptococcus pneumoniae Containing the Erythromycin Efflux Resistance Gene mef(I) and the Chloramphenicol Resistance Gene catQ". Antimicrobial Agents and Chemotherapy 51, n.º 11 (20 de agosto de 2007): 3983–87. http://dx.doi.org/10.1128/aac.00790-07.

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ABSTRACT In recent years mef genes, encoding efflux pumps responsible for M-type macrolide resistance, have been investigated extensively for streptococci. mef(I) is a recently described mef variant detected in particular isolates of Streptococcus pneumoniae instead of the more common mef(E) and mef(A). This study shows that mef(I) is located in a new composite genetic element, whose sequence was completely analyzed and the left and right junctions determined, demonstrating a unique genetic organization. The new composite structure (30,505 bp), designated the 5216IQ complex, consists of two halves: a left one (15,316 bp) formed by parts of the known transposons Tn5252 and Tn916, and a right one (15,115 bp) formed by a new fragment, designated the IQ element. While the defective Tn916 contained a silent tet(M) gene, the IQ element, ending with identical transposase genes on both sides and containing the mef(I) gene with an adjacent new msr(D) gene variant and a catQ chloramphenicol acetyltransferase gene, was completely different from the genetic elements carrying other mef genes in pneumococci. This is the first report demonstrating catQ in S. pneumoniae and showing its linkage with a mef gene. Analysis of the chromosomal region beyond the left junction revealed an organization more similar to that of S. pneumoniae strain TIGR4 than to that of strain R6. The 5216IQ complex was apparently nonmobile, with no detectable transfer of erythromycin resistance being obtained in repeated transformation and conjugation assays.

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Cochetti, Ileana, Manuela Vecchi, Marina Mingoia, Emily Tili, Maria R. Catania, Aldo Manzin, Pietro E. Varaldo y Maria Pia Montanari. "Molecular Characterization of Pneumococci with Efflux-Mediated Erythromycin Resistance and Identification of a Novel mef Gene Subclass, mef(I)". Antimicrobial Agents and Chemotherapy 49, n.º 12 (diciembre de 2005): 4999–5006. http://dx.doi.org/10.1128/aac.49.12.4999-5006.2005.

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ABSTRACT The molecular genetics of macrolide resistance were analyzed in 49 clinical pneumococci (including an “atypical” bile-insoluble strain currently assigned to the new species Streptococcus pseudopneumoniae) with efflux-mediated erythromycin resistance (M phenotype). All test strains had the mef gene, identified as mef(A) in 30 isolates and mef(E) in 19 isolates (including the S. pseudopneumoniae strain) on the basis of PCR-restriction fragment length polymorphism analysis. Twenty-eight of the 30 mef(A) isolates shared a pulsed-field gel electrophoresis (PFGE) type corresponding to the England14-9 clone. Of those isolates, 27 (20 belonging to serotype 14) yielded multilocus sequence type ST9, and one isolate yielded a new sequence type. The remaining two mef(A) isolates had different PFGE types and yielded an ST9 type and a new sequence type. Far greater heterogeneity was displayed by the 19 mef(E) isolates, which fell into 11 PFGE types, 12 serotypes (though not serotype 14), and 12 sequence types (including two new ones and an undetermined type for the S. pseudopneumoniae strain). In all mef(A) pneumococci, the mef element was a regular Tn1207.1 transposon, whereas of the mef(E) isolates, 17 carried the mega element and 2 exhibited a previously unreported organization, with no PCR evidence of the other open reading frames of mega. The mef gene of these two isolates, which did not match with the mef(E) gene of the mega element (93.6% homology) and which exhibited comparable homology (91.4%) to the mef(A) gene of the Tn1207.1 transposon, was identified as a novel mef gene variant and was designated mef(I). While penicillin-nonsusceptible isolates (three resistant isolates and one intermediate isolate) were all mef(E) strains, tetracycline resistance was also detected in three mef(A) isolates, due to the tet(M) gene carried by a Tn916-like transposon. A similar mechanism accounted for resistance in four of the five tetracycline-resistant isolates carrying mef(E), in three of which mega was inserted in the Tn916-like transposon, giving rise to the composite element Tn2009. In the fifth mef(E)-positive tetracycline-resistant isolate (the S. pseudopneumoniae strain), tetracycline resistance was due to the presence of the tet(O) gene, apparently unlinked to mef(E).

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Wierzbowski, Aleksandra K., Dave Boyd, Michael Mulvey, Daryl J. Hoban y George G. Zhanel. "Expression of the mef(E) Gene Encoding the Macrolide Efflux Pump Protein Increases in Streptococcus pneumoniae with Increasing Resistance to Macrolides". Antimicrobial Agents and Chemotherapy 49, n.º 11 (noviembre de 2005): 4635–40. http://dx.doi.org/10.1128/aac.49.11.4635-4640.2005.

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ABSTRACT Active macrolide efflux is a major mechanism of macrolide resistance in Streptococcus pneumoniae in many parts of the world, especially North America. In Canada, this active macrolide efflux in S. pneumoniae is predominantly due to acquisition of the mef(E) gene. In the present study, we assessed the mef(E) gene sequence as well as mef(E) expression in variety of low- and high-level macrolide-resistant, clindamycin-susceptible (M-phenotype) S. pneumoniae isolates (erythromycin MICs, 1 to 32 μg/ml; clindamycin MICs, ≤0.25 μg/ml). Southern blot hybridization with mef(E) probe and EcoRI digestion and relative real-time reverse transcription-PCR were performed to study the mef(E) gene copy number and expression. Induction of mef(E) expression was analyzed by Etest susceptibility testing pre- and postincubation with subinhibitory concentrations of erythromycin, clarithromycin, azithromycin, telithromycin, and clindamycin. The macrolide efflux gene, mef(E), was shown to be a single-copy gene in all 23 clinical S. pneumoniae isolates tested, and expression post-macrolide induction increased 4-, 6-, 20-, and 200-fold in isolates with increasing macrolide resistance (erythromycin MICs 2, 4, 8, and 32 μg/ml, respectively). Sequencing analysis of the macrolide efflux genetic assembly (mega) revealed that mef(E) had a 16-bp deletion 153 bp upstream of the putative start codon in all 23 isolates. A 119-bp intergenic region between mef(E) and mel was sequenced, and a 99-bp deletion was found in 11 of the 23 M-phenotype S. pneumoniae isolates compared to the published mega sequence. However, the mef(E) gene was fully conserved among both high- and low-level macrolide-resistant isolates. In conclusion, increased expression of mef(E) is associated with higher levels of macrolide resistance in macrolide-resistant S. pneumoniae.

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Cerdá Zolezzi, Paula, Leticia Millán Laplana, Carmen Rubio Calvo, Pilar Goñi Cepero, Melisa Canales Erazo y Rafael Gómez-Lus. "Molecular Basis of Resistance to Macrolides and Other Antibiotics in Commensal Viridans Group Streptococci and Gemella spp. and Transfer of Resistance Genes to Streptococcus pneumoniae". Antimicrobial Agents and Chemotherapy 48, n.º 9 (septiembre de 2004): 3462–67. http://dx.doi.org/10.1128/aac.48.9.3462-3467.2004.

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ABSTRACT We assessed the mechanisms of resistance to macrolide-lincosamide-streptogramin B (MLSB) antibiotics and related antibiotics in erythromycin-resistant viridans group streptococci (n = 164) and Gemella spp. (n = 28). The macrolide resistance phenotype was predominant (59.38%); all isolates with this phenotype carried the mef(A) or mef(E) gene, with mef(E) being predominant (95.36%). The erm(B) gene was always detected in strains with constitutive and inducible MLSB resistance and was combined with the mef(A/E) gene in 47.44% of isolates. None of the isolates carried the erm(A) subclass erm(TR), erm(A), or erm(C) genes. The mel gene was detected in all but four strains carrying the mef(A/E) gene. The tet(M) gene was found in 86.90% of tetracycline-resistant isolates and was strongly associated with the presence of the erm(B) gene. The catpC194 gene was detected in seven chloramphenicol-resistant Streptococcus mitis isolates, and the aph(3′)-III gene was detected in four viridans group streptococcal isolates with high-level kanamycin resistance. The intTn gene was found in all isolates with the erm(B), tet(M), aph(3′)-III, and catpC194 gene. The mef(E) and mel genes were successfully transferred from both groups of bacteria to Streptococcus pneumoniae R6 by transformation. Viridans group streptococci and Gemella spp. seem to be important reservoirs of resistance genes.

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Ando, Koji, Emi Matsuo, Kensuke Horio, Shinya Tominaga, Daisuke Imanishi, Yoshitaka Imaizumi, Hideki Tsushima et al. "Transcriptional Activity of MEF/ELF4 on the HDM2 Promoter Is Enhanced by the Mutation of the NPM1 Gene". Blood 116, n.º 21 (19 de noviembre de 2010): 179. http://dx.doi.org/10.1182/blood.v116.21.179.179.

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Abstract Abstract 179 Background: MEF/ELF4 belongs to an ETS family of transcription factors that has roles in hematopoietic stem cells (HSCs): in a Mef-null mouse model, HSC increased residence in G0 status of the cell cycle. It was also reported that Mef/Elf4 promoted the transformation of fibroblasts by inhibiting two major tumor suppressor pathways, the p53 and p16/Rb pathways, inducing the expression of the Mdm2 gene. Our previous study on AML samples showed that the expression of MEF/ELF4 was significantly lower in cases with t(8;21) and t(15;17) compared with those with normal karyotype (AML-NK). However, little has been investigated about the role of MEF/ELF4 in AML-NK. Objective: The aim of the present study is to elucidate how MEF/ELF4 works and is controlled in AML-NK. Methods: We identified the associated protein with MEF/ELF4 using the Tandem affinity purification (TAP) method followed by MASS analysis. Transforming activity of MEF/ELF4 was tested by colony-formation assay using NIH3T3 cells. The transcriptional activity of MEF/ELF4 and its binding to the HDM2 promoter region, with or without wild type NPM1 (wtNPM1) and its mutants (mutNPM1), were examined using luciferase analysis, EMSA and ChIP assay. We also examined the expression of MEF/ELF4 and HDM2 in CD34-positive AML-NK cells obtained from 22 patients. Results: Nucleophosmin (NPM1) was included in the twenty-six proteins that were found in the TAP analysis, and the direct binding between MEF/ELF4 and NPM1 was confirmed by immunoprecipitation, GST pull down, and in vitro translation assays. Transforming activity of MEF/ELF4 was decreased 3-fold by the overexpression of wild-type NPM1, whereas the activity was enhanced by mutNPM1. Transcriptional activity of MEF/ELF4 measured using luciferase assay (159-fold by arbitral unit) was increased by the co-expression of mutNPM1 (315-fold), and decreased by wtNPM1 (109-fold) (Figure1). Forced expression of siRNA for NPM1 enhanced the luciferase activity of MEF/ELF4. These results indicated that the transactivating activity of MEF/ELF4 was enhanced by mutNPM1, and decreased by wtNPM1. EMSA and ChIP assay for the HDM2 promoter demonstrated that MEF/ELF4 was bound to the specific binding sites of the HDM2 gene. wtNPM1 weakened the binding of MEF/ELF4 to the promoter of the HDM2 gene in EMSA and ChIP assay. However, co-expression of mutNPM1 increased its binding to the HDM2 promoter in ChIP assay (Figure2). These data suggested that NPM1 regulated the binding of MEF/ELF4 to the HDM2 promoter, which influenced the activity of MEF/ELF4. In clinical samples, AML-NK cells with the high expression of MEF/ELF4 showed significantly higher expression of HDM2 than those with the low expression of MEF/ELF4 (P=0.009). In AML-NK cases with the mutated-NPM1 gene, the expression of HDM2 was higher than those with the wild-type NPM1 (P=0.03). Conclusion: These data suggested that MEF/ELF4 activates the expression of the HDM2 gene under the influence of the mutational status of the NPM1 gene in AML-NK. Disclosures: No relevant conflicts of interest to declare.

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Cserjesi, P. y E. N. Olson. "Myogenin induces the myocyte-specific enhancer binding factor MEF-2 independently of other muscle-specific gene products". Molecular and Cellular Biology 11, n.º 10 (octubre de 1991): 4854–62. http://dx.doi.org/10.1128/mcb.11.10.4854-4862.1991.

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The myocyte-specific enhancer-binding factor MEF-2 is a nuclear factor that interacts with a conserved element in the muscle creatine kinase and myosin light-chain 1/3 enhancers (L. A. Gossett, D. J. Kelvin, E. A. Sternberg, and E. N. Olson, Mol. Cell. Biol. 9:5022-5033, 1989). We show in this study that MEF-2 is regulated by the myogenic regulatory factor myogenin and that mitogenic signals block this regulatory interaction. Induction of MEF-2 by myogenin occurs in transfected 10T1/2 cells that have been converted to myoblasts by myogenin, as well as in CV-1 kidney cells that do not activate the myogenic program in response to myogenin. Through mutagenesis of the MEF-2 site, we further defined the binding site requirements for MEF-2 and identified potential MEF-2 sites within numerous muscle-specific regulatory regions. The MEF-2 site was also found to bind a ubiquitous nuclear factor whose binding specificity was similar to but distinct from that of MEF-2. Our results reveal that MEF-2 is controlled, either directly or indirectly, by a myogenin-dependent regulatory pathway and suggest that growth factor signals suppress MEF-2 expression through repression of myogenin expression or activity. The ability of myogenin to induce MEF-2 activity in CV-1 cells, which do not activate downstream genes associated with terminal differentiation, also demonstrates that myogenin retains limited function within cell types that are nonpermissive for myogenesis and suggests that MEF-2 is regulated independently of other muscle-specific genes.

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Cserjesi, P. y E. N. Olson. "Myogenin induces the myocyte-specific enhancer binding factor MEF-2 independently of other muscle-specific gene products." Molecular and Cellular Biology 11, n.º 10 (octubre de 1991): 4854–62. http://dx.doi.org/10.1128/mcb.11.10.4854.

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The myocyte-specific enhancer-binding factor MEF-2 is a nuclear factor that interacts with a conserved element in the muscle creatine kinase and myosin light-chain 1/3 enhancers (L. A. Gossett, D. J. Kelvin, E. A. Sternberg, and E. N. Olson, Mol. Cell. Biol. 9:5022-5033, 1989). We show in this study that MEF-2 is regulated by the myogenic regulatory factor myogenin and that mitogenic signals block this regulatory interaction. Induction of MEF-2 by myogenin occurs in transfected 10T1/2 cells that have been converted to myoblasts by myogenin, as well as in CV-1 kidney cells that do not activate the myogenic program in response to myogenin. Through mutagenesis of the MEF-2 site, we further defined the binding site requirements for MEF-2 and identified potential MEF-2 sites within numerous muscle-specific regulatory regions. The MEF-2 site was also found to bind a ubiquitous nuclear factor whose binding specificity was similar to but distinct from that of MEF-2. Our results reveal that MEF-2 is controlled, either directly or indirectly, by a myogenin-dependent regulatory pathway and suggest that growth factor signals suppress MEF-2 expression through repression of myogenin expression or activity. The ability of myogenin to induce MEF-2 activity in CV-1 cells, which do not activate downstream genes associated with terminal differentiation, also demonstrates that myogenin retains limited function within cell types that are nonpermissive for myogenesis and suggests that MEF-2 is regulated independently of other muscle-specific genes.

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Cousin, Sydney, William L. H. Whittington y Marilyn C. Roberts. "Acquired Macrolide Resistance Genes in Pathogenic Neisseria spp. Isolated between 1940 and 1987". Antimicrobial Agents and Chemotherapy 47, n.º 12 (diciembre de 2003): 3877–80. http://dx.doi.org/10.1128/aac.47.12.3877-3880.2003.

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ABSTRACT Seventy-six Neisseria gonorrhoeae isolates, isolated between 1940 and 1987, and seven Neisseria meningitidis isolates, isolated between 1963 and 1987, were screened for the presence of acquired mef(A), erm(B), erm(C), and erm(F) genes by using DNA-DNA hybridization, PCR analysis, and sequencing. The mef(A), erm(B), and erm(F) genes were all identified in a 1955 N. gonorrhoeae isolate, while the erm(C) gene was identified in a 1963 N. gonorrhoeae isolate. Similarly, both the mef(A) and erm(F) genes were identified in a 1963 N. meningitidis isolate. All four acquired genes were found in later isolates of both species. The mef(A) gene from a 1975 N. gonorrhoeae isolate was sequenced and had 100% DNA and amino acid identity with the mef(A) gene from a 1990s Streptococcus pneumoniae isolate. Selected early isolates were able to transfer their acquired genes to an Enterococcus faecalis recipient, suggesting that these genes are associated with conjugative transposons. These isolates are the oldest of any species to carry the mef(A) gene and among the oldest to carry these erm genes.

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Hidaka, K., I. Yamamoto, Y. Arai y T. Mukai. "The MEF-3 motif is required for MEF-2-mediated skeletal muscle-specific induction of the rat aldolase A gene". Molecular and Cellular Biology 13, n.º 10 (octubre de 1993): 6469–78. http://dx.doi.org/10.1128/mcb.13.10.6469-6478.1993.

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The rat aldolase A gene contains two alternative promoters and two alternative first exons. The distal promoter M is expressed at a high level only in skeletal muscle. Previous in vitro transfection studies identified the region from -202 to -85 as an enhancer that is responsible for dramatic activation during the differentiation of chicken primary myoblasts. This enhancer contains an A/T-rich sequence resembling the MEF-2 motif, which is an important element of muscle enhancers and promoters. In this study, we demonstrate that the MEF-2 sequence is essential but not sufficient for the activity of the enhancer. Another region required for the activity was recognized by a nuclear factor, tentatively named MAF1. MAF1 was found in both muscle cells and nonmuscle cells, and MAF1 from both cell types was indistinguishable by gel retardation and DNase I footprint experiments. The sequence required for MAF1 binding is very similar to the MEF-3 motif, which is an element of the skeletal muscle-specific enhancer of the cardiac troponin C gene. Because MAF1 and MEF-3 are closely related in both recognition sequence and distribution, MAF1 and MEF-3 probably represent the same nuclear factor which may play an important role in muscle gene transcription. Thus, the muscle-specific induction of the aldolase A gene is governed by muscle-specific MEF-2 and existing MEF-3 (MAF1).

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Hidaka, K., I. Yamamoto, Y. Arai y T. Mukai. "The MEF-3 motif is required for MEF-2-mediated skeletal muscle-specific induction of the rat aldolase A gene." Molecular and Cellular Biology 13, n.º 10 (octubre de 1993): 6469–78. http://dx.doi.org/10.1128/mcb.13.10.6469.

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The rat aldolase A gene contains two alternative promoters and two alternative first exons. The distal promoter M is expressed at a high level only in skeletal muscle. Previous in vitro transfection studies identified the region from -202 to -85 as an enhancer that is responsible for dramatic activation during the differentiation of chicken primary myoblasts. This enhancer contains an A/T-rich sequence resembling the MEF-2 motif, which is an important element of muscle enhancers and promoters. In this study, we demonstrate that the MEF-2 sequence is essential but not sufficient for the activity of the enhancer. Another region required for the activity was recognized by a nuclear factor, tentatively named MAF1. MAF1 was found in both muscle cells and nonmuscle cells, and MAF1 from both cell types was indistinguishable by gel retardation and DNase I footprint experiments. The sequence required for MAF1 binding is very similar to the MEF-3 motif, which is an element of the skeletal muscle-specific enhancer of the cardiac troponin C gene. Because MAF1 and MEF-3 are closely related in both recognition sequence and distribution, MAF1 and MEF-3 probably represent the same nuclear factor which may play an important role in muscle gene transcription. Thus, the muscle-specific induction of the aldolase A gene is governed by muscle-specific MEF-2 and existing MEF-3 (MAF1).

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Lacorazza, H. Daniel, Serena Lopiccolo, Eric Rubenstein, Yan Liu, Juliana Nunes, Henrik Hasle, Bengt Fadeel, Kim Ericson, Jan-Inge Henter y Stephen D. Nimer. "Identification of a MEF Gene Mutation in a Familial Hemophagocytic Lymphohistiocytosis Patient That Decreases MEF Transcriptional Activity." Blood 106, n.º 11 (16 de noviembre de 2005): 3013. http://dx.doi.org/10.1182/blood.v106.11.3013.3013.

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Abstract Familial hemophagocytic lymphohistiocytosis (FHL) is generally an autosomal recessive disease of early childhood characterized by uncontrolled T cell and macrophage activation leading to a fatal accumulation of activated T lymphocytes and histiocytes in different tissues. Immune regulation is severely impaired in these patients (both CTL and NK cells) and defects in perforin gene expression, an important component of the lytic granules, were the first defects identified in these patients. So far, FHL genetics have identified a locus at chromosome 9q22 (not molecularly defined yet), at chromosome 10q21-22 (where mutations in perforin gene have been described in 20% of FHL patients), at chromosome 17q25 (where mutations in the Munc13-4 gene have been found) and most recently at chromosome 6q24 (where mutations in the syntaxin-11 gene have been found). We described previously that MEF-null mice, which lack the ETS-transcription factor also known as ELF-4 (located at Xq26.1), have impaired NK cell development and function, and no NK cell perforin gene expression. We also showed that MEF regulates the human perforin proximal promoter via two ETS binding sites and showed that MEF is bound to the perforin promoter in vivo, using chromatin immunoprecipitation. Subsequently, we initiated a study of MEF gene integrity in male patients that have been studied and lacked perforin gene mutations. In addition to a known polymorphism in exon 9 (503 C→T) present in approximately 30% of unrelated patients and leukemic cell lines, we found a nucleotide change in exon 9 of MEF (408, C→T) in a male FHL patient from Denmark. The mutation found in the son, who was diagnosed with FHL and received a BMT at 12 years of age, was also seen in the patient’s grandmother, mother and one sister (heterozygous). Mutation 408 leads to an amino acid change (Val→Met) in a region located between the Ser/Thr and Pro rich domains in the C-terminal portion of MEF. We generated a MEF-mutant (MEFVal→Met) protein; it has a reduced capacity to activate the perforin gene promoter (only 30–40% of the wild type). MEFVal→Met does not have a dominant negative effect, when co-transfected with wild type protein, which could account for the FHL phenotype found in the male only. We are further examining the biology of this mutation in MEF-null cells to see if it can contribute to FHL pathology. Transcription factor abnormalities, such as the MEF mutation in this family, should be evaluated to help explain the pathogenesis of FHL in different patients.

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Giovanetti, Eleonora, Andrea Brenciani, Remo Lupidi, Marilyn C. Roberts y Pietro E. Varaldo. "Presence of the tet(O) Gene in Erythromycin- and Tetracycline-Resistant Strains of Streptococcus pyogenes and Linkage with either the mef(A) or the erm(A) Gene". Antimicrobial Agents and Chemotherapy 47, n.º 9 (septiembre de 2003): 2844–49. http://dx.doi.org/10.1128/aac.47.9.2844-2849.2003.

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ABSTRACT Sixty-three recent Italian clinical isolates of Streptococcus pyogenes resistant to both erythromycin (MICs ≥ 1 μg/ml) and tetracycline (MICs ≥ 8 μg/ml) were genotyped for macrolide and tetracycline resistance genes. We found 19 isolates carrying the mef(A) and the tet(O) genes; 25 isolates carrying the erm(A) and tet(O) genes; and 2 isolates carrying the erm(A), tet(M), and tet(O) genes. The resistance of all erm(A)-containing isolates was inducible, but the isolates could be divided into two groups on the basis of erythromycin MICs of either >128 or 1 to 4 μg/ml. The remaining 17 isolates included 15 isolates carrying the erm(B) gene and 2 isolates carrying both the erm(B) and the mef(A) genes, with all 17 carrying the tet(M) gene. Of these, 12 carried Tn916-Tn1545-like conjugative transposons. Conjugal transfer experiments demonstrated that the tet(O) gene moved with and without the erm(A) gene and with the mef(A) gene. These studies, together with the results of pulsed-field gel electrophoresis experiments and hybridization assays with DNA probes specific for the tet(O), erm(A), and mef(A) genes, suggested a linkage of tet(O) with either erm(A) or mef(A) in erythromycin- and tetracycline-resistant S. pyogenes isolates. By amplification and sequencing experiments, we detected the tet(O) gene ca. 5.5 kb upstream from the mef(A) gene. This is the first report demonstrating the presence of the tet(O) gene in S. pyogenes and showing that it may be linked with another gene and can be moved by conjugation from one chromosome to another.

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Luna, Vicki A., Sydney Cousin, William L. H. Whittington y Marilyn C. Roberts. "Identification of the Conjugative mefGene in Clinical Acinetobacter junii and Neisseria gonorrhoeae Isolates". Antimicrobial Agents and Chemotherapy 44, n.º 9 (1 de septiembre de 2000): 2503–6. http://dx.doi.org/10.1128/aac.44.9.2503-2506.2000.

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ABSTRACT The mef gene, originally described for gram-positive organisms and coding for an efflux pump, has been identified in clinical isolates of Acinetobacter junii andNeisseria gonorrhoeae. These strains could transfer themef gene at frequencies ranging from 10−6 to 10−9 into one or more of the following recipients: gram-negative Moraxella catarrhalis, Neisseria perflava/sicca and Neisseria mucosa and gram-positiveEnterococcus faecalis. Three Streptococcus pneumoniae strains could transfer the mef gene intoEikenella corrodens, Haemophilus influenzae,Kingella denitrificans, M. catarrhalis,Neisseria meningitidis, N. perflava/sicca, andN. mucosa at similar frequencies. The mef gene can thus be transferred to and expressed in a variety of gram-negative recipients.

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Nakatsuji, Y., K. Hidaka, S. Tsujino, Y. Yamamoto, T. Mukai, T. Yanagihara, T. Kishimoto y S. Sakoda. "A single MEF-2 site is a major positive regulatory element required for transcription of the muscle-specific subunit of the human phosphoglycerate mutase gene in skeletal and cardiac muscle cells". Molecular and Cellular Biology 12, n.º 10 (octubre de 1992): 4384–90. http://dx.doi.org/10.1128/mcb.12.10.4384-4390.1992.

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In order to analyze the transcriptional regulation of the muscle-specific subunit of the human phosphoglycerate mutase (PGAM-M) gene, chimeric genes composed of the upstream region of the PGAM-M gene and the bacterial chloramphenicol acetyltransferase (CAT) gene were constructed and transfected into C2C12 skeletal myocytes, primary cultured cardiac muscle cells, and C3H10T1/2 fibroblasts. The expression of chimeric reporter genes was restricted in skeletal and cardiac muscle cells. In C2C12 myotubes and primary cultured cardiac muscle cells, the segment between nucleotides -165 and +41 relative to the transcription initiation site was sufficient to confer maximal CAT activity. This region contains two E boxes and one MEF-2 motif. Deletion and substitution mutation analysis showed that a single MEF-2 motif but not the E boxes had a substantial effect on skeletal and cardiac muscle-specific enhancer activity and that the cardiac muscle-specific negative regulatory region was located between nucleotides -505 and -165. When the PGAM-M gene constructs were cotransfected with MyoD into C3H10T1/2, the profile of CAT activity was similar to that observed in C2C12 myotubes. Gel mobility shift analysis revealed that when the nuclear extracts from skeletal and cardiac muscle cells were used, the PGAM-M MEF-2 site generated the specific band that was inhibited by unlabeled PGAM-M MEF-2 and muscle creatine kinase MEF-2 oligomers but not by a mutant PGAM-M MEF-2 oligomer. These observations define the PGAM-M enhancer as the only cardiac- and skeletal-muscle-specific enhancer characterized thus far that is mainly activated through MEF-2.

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16

Nakatsuji, Y., K. Hidaka, S. Tsujino, Y. Yamamoto, T. Mukai, T. Yanagihara, T. Kishimoto y S. Sakoda. "A single MEF-2 site is a major positive regulatory element required for transcription of the muscle-specific subunit of the human phosphoglycerate mutase gene in skeletal and cardiac muscle cells." Molecular and Cellular Biology 12, n.º 10 (octubre de 1992): 4384–90. http://dx.doi.org/10.1128/mcb.12.10.4384.

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In order to analyze the transcriptional regulation of the muscle-specific subunit of the human phosphoglycerate mutase (PGAM-M) gene, chimeric genes composed of the upstream region of the PGAM-M gene and the bacterial chloramphenicol acetyltransferase (CAT) gene were constructed and transfected into C2C12 skeletal myocytes, primary cultured cardiac muscle cells, and C3H10T1/2 fibroblasts. The expression of chimeric reporter genes was restricted in skeletal and cardiac muscle cells. In C2C12 myotubes and primary cultured cardiac muscle cells, the segment between nucleotides -165 and +41 relative to the transcription initiation site was sufficient to confer maximal CAT activity. This region contains two E boxes and one MEF-2 motif. Deletion and substitution mutation analysis showed that a single MEF-2 motif but not the E boxes had a substantial effect on skeletal and cardiac muscle-specific enhancer activity and that the cardiac muscle-specific negative regulatory region was located between nucleotides -505 and -165. When the PGAM-M gene constructs were cotransfected with MyoD into C3H10T1/2, the profile of CAT activity was similar to that observed in C2C12 myotubes. Gel mobility shift analysis revealed that when the nuclear extracts from skeletal and cardiac muscle cells were used, the PGAM-M MEF-2 site generated the specific band that was inhibited by unlabeled PGAM-M MEF-2 and muscle creatine kinase MEF-2 oligomers but not by a mutant PGAM-M MEF-2 oligomer. These observations define the PGAM-M enhancer as the only cardiac- and skeletal-muscle-specific enhancer characterized thus far that is mainly activated through MEF-2.

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17

Tiemei, Zhao, Fang Xiangqun y Liu Youning. "Resistance Phenotypes and Genotypes of Erythromycin-Resistant Streptococcus pneumoniae Isolates in Beijing and Shenyang, China". Antimicrobial Agents and Chemotherapy 48, n.º 10 (octubre de 2004): 4040–41. http://dx.doi.org/10.1128/aac.48.10.4040-4041.2004.

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ABSTRACT Of a total of 192 Streptococcus pneumoniae isolates, 149 (77.6%) were not susceptible to erythromycin. Of these 149 isolates, 117 (79.1%) contained the erm(B) gene, 16 (10.8%) contained the mef(A) gene, and 15 (10.1%) harbored both the erm(B) and mef(A) genes.

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18

Tretiakova, Anna, Jessica Otte, Sidney E. Croul, Julie H. Kim, Edward M. Johnson, Shohreh Amini y Kamel Khalili. "Association of JC Virus Large T Antigen with Myelin Basic Protein Transcription Factor (MEF-1/Purα) in Hypomyelinated Brains of Mice Transgenically Expressing T Antigen". Journal of Virology 73, n.º 7 (1 de julio de 1999): 6076–84. http://dx.doi.org/10.1128/jvi.73.7.6076-6084.1999.

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ABSTRACT Progressive multifocal leukoencephalopathy (PML) is a fatal demyelinating disease caused by cytolytic destruction of oligodendrocytes, the myelin-producing cells of the central nervous system, by the human neurotropic JC virus (JCV). The early protein of JCV, T antigen, which is produced at the early stage of infection, is important for orchestrating the events leading to viral lytic infection and cytolytic destruction of oligodendrocytes. Results from transgenic mouse studies, however, have revealed that, in the absence of lytic infection, this protein can induce brain hypomyelination and suppression of myelin gene expression. Since expression of the gene encoding myelin basic protein, the major component of myelin, can be regulated by a DNA-binding transcription factor, MEF-1/Purα, (Purα), we have examined the level of this protein in transgenic mouse brains. Results from immunoprecipitation and Western blots showed that while there was no drastic decrease in the level of MEF-1/Purα in transgenic mouse brains, JCV T antigen was found in a complex with MEF-1/Purα. Immunohistological studies revealed abnormal oligodendrocytes in white matter, where MEF-1/Purα and T antigen were detected. Furthermore, immunogold electron microscopic studies revealed that Purα and T antigen are colocalized in the nucleus of the oligodendrocytes and in hippocampal neurons. Interestingly, results from cell culture studies revealed that incubation of oligodendrocytes with JCV led to a drastic decrease in the level of MEF-1/Purα protein. These observations provide insight into the molecular pathogenesis of PML and support a model for a dual effect of JCV on inducing hypomyelination by (i) affecting myelin gene expression via interaction of JCV T antigen and the myelin gene transcription factor, MEF-1/Purα, and (ii) causing a decline in the level of the host regulatory proteins, including MEF-1/Purα, which are involved in myelin gene expression.

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19

Yang, Xinhai, Jonathan S. T. Sham, M. H. Ng, Sai-Wah Tsao, Dekai Zhang, Scott W. Lowe y Liang Cao. "LMP1 of Epstein-Barr Virus Induces Proliferation of Primary Mouse Embryonic Fibroblasts and Cooperatively Transforms the Cells with a p16-Insensitive CDK4 Oncogene". Journal of Virology 74, n.º 2 (15 de enero de 2000): 883–91. http://dx.doi.org/10.1128/jvi.74.2.883-891.2000.

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ABSTRACT The latent membrane protein LMP1 of Epstein-Barr virus (EBV) is often present in EBV-associated malignancies including nasopharyngeal carcinoma and Hodgkin's lymphoma. Previous work demonstrates that the LMP1 gene of EBV is sufficient to transform certain established rodent fibroblast cell lines and to induce the tumorigenicity of some human epithelial cell lines. In addition, LMP1 plays pleiotropic roles in cell growth arrest, differentiation, and apoptosis, depending on the background of the target cells. To examine the roles of LMP1 in cell proliferation and growth regulation in primary culture cells, we constructed a recombinant retrovirus containing an LMP1 gene. With this retrovirus, LMP1 was shown to stimulate the proliferation of primary mouse embryonic fibroblasts (MEF cells). It has a mitogenic activity for MEF cells, as demonstrated by an immediate induction of cell doubling time. In addition, it significantly extends the passage number of MEF cells to more than 30 after retroviral infection, compared with less than 5 for uninfected MEF cells. Furthermore, LMP1 cooperates with a p16-insensitive CDK4 R24C oncogene in transforming MEF cells. Our results provide the first evidence of the abilities of the LMP1 gene, acting alone, to effectively induce the proliferation of primary MEF cells and of its cooperativity with another cellular oncogene in transforming primary cells.

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20

Chihara, T., H. Kai, A. Hisatsune, C. B. Basbaum, A. Uto, A. Kokusho, T. Koyanagi y T. Miyata. "MEF TRANSACTIVATES LYSOZYME GENE IN TRACHEAL EPITHELIAL CELLS". Japanese Journal of Pharmacology 76 (1998): 88. http://dx.doi.org/10.1016/s0021-5198(19)40470-8.

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21

Zolezzi, Paula Cerdá, Pilar Goñi Cepero, Joaquim Ruiz, Leticia Millán Laplana, Carmen Rubio Calvo y Rafael Gómez-Lus. "Molecular Epidemiology of Macrolide and Tetracycline Resistances in Commensal Gemella sp. Isolates". Antimicrobial Agents and Chemotherapy 51, n.º 4 (5 de febrero de 2007): 1487–90. http://dx.doi.org/10.1128/aac.01374-06.

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ABSTRACT The epidemiologic relatedness of 29 erythromycin-resistant Gemella sp. strains from normal flora, characterized previously, were evaluated by pulsed-field gel electrophoresis (PFGE). Three isolates carried the tet(O) gene and the tet(M) gene. The msr(A) gene was found in two Gemella morbillorum strains in combination with the erm(B) or mef(E) gene. The sequences of the mef(A/E), erm(B), and msr(A) genes showed a high similarity to the corresponding sequences of other gram-positive cocci. All the strains harboring the mef(A/E) gene and the msr(D) gene possessed open reading frame 3 (ORF3)/ORF6. The 16 G. morbillorum isolates represented 15 distinct DNA profiles. Four clusters were identified (≥80% genetic relatedness). The 12 Gemella haemolysans strains belonged to different PFGE types. The clonal diversity found suggests that horizontal transfer may be the main route through which erythromycin resistance is acquired.

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22

de la Pedrosa, Elia Gómez G., María-Isabel Morosini, Mark van der Linden, Patricia Ruiz-Garbajosa, Juan Carlos Galán, Fernando Baquero, Ralf René Reinert y Rafael Cantón. "Polyclonal Population Structure of Streptococcus pneumoniae Isolates in Spain Carrying mef and mef plus erm(B)". Antimicrobial Agents and Chemotherapy 52, n.º 6 (24 de marzo de 2008): 1964–69. http://dx.doi.org/10.1128/aac.01487-07.

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ABSTRACT The population structure (serotypes, pulsed-field gel electrophoresis [PFGE] types, and multilocus sequencing types) of 45 mef-positive Streptococcus pneumoniae isolates [carrying mef alone (n = 17) or with the erm(B) gene n = 28)] were studied. They were selected from among all erythromycin-resistant isolates (n = 244) obtained from a collection of 712 isolates recovered from different Spanish geographic locations in the prevaccination period from 1999 to 2003. The overall rates of resistance (according to the criteria of the CLSI) among the 45 mef-positive isolates were as follows: penicillin G, 82.2%; cefotaxime, 22.2%; clindamycin, 62.2%; and tetracycline, 68.8% [mainly in isolates carrying erm(B) plus mef(E); P < 0.001]. No levofloxacin or telithromycin resistance was found. Macrolide resistance phenotypes (as determined by the disk diffusion approximation test) were 37.7% for macrolide resistance [with all but one due to mef(E)] and 62.2% for constitutive macrolide-lincosamide-streptogramin B resistance [cMLSB; with all due to mef(E) plus erm(B)]. Serotypes 14 (22.2%), 6B (17.7%), 19A (13.3%), and 19F (11.1%) were predominant. Twenty-five different DNA patterns (PFGE types) were observed. Our mef-positive isolates were grouped (by eBURST analysis) into four clonal complexes (n = 18) and 19 singleton clones (n = 27). With the exception of clone Spain9V-3, all clonal complexes (clonal complexes 6B, Spain6B-2, and Sweden15A-25) and 73.6% of singleton clones carried both the erm(B) and the mef(E) genes. The international multiresistant clones Spain23F-1 and Poland6B-20 were represented as singleton clones. A high proportion of mef-positive S. pneumoniae isolates presented the erm(B) gene, with all isolates expressing the cMLSB phenotype. A polyclonal population structure was demonstrated within our Spanish mef-positive S. pneumoniae isolates, with few clonal complexes overrepresented within this collection.

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23

Goswami, S., P. Qasba, S. Ghatpande, S. Carleton, A. K. Deshpande, M. Baig y M. A. Siddiqui. "Differential expression of the myocyte enhancer factor 2 family of transcription factors in development: the cardiac factor BBF-1 is an early marker for cardiogenesis". Molecular and Cellular Biology 14, n.º 8 (agosto de 1994): 5130–38. http://dx.doi.org/10.1128/mcb.14.8.5130-5138.1994.

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In the present study, we have used single chicken blastoderms of defined early developmental stages, beginning with the prestreak stage, stage 1 (V. Hamburger and H. L. Hamilton, J. Morphol. 88:49-92, 1951), to analyze the onset of cardiac myogenesis by monitoring the appearance of selected cardiac muscle tissue-specific gene transcripts and the functional expression of the myocyte enhancer factor 2 (MEF-2) proteins. Using gene-specific oligonucleotide primers in reverse transcriptase PCR assay, we have demonstrated that the cardiac myosin light-chain 2 (MLC2) and alpha-actin gene transcripts appear as early as stage 5, i.e., immediately after the cardiogenic fate assignment at stage 4. Consistent with this observation is the developmental expression pattern of DNA-binding activity of BBF-1, a cardiac muscle-specific member of the MEF-2 protein family, which also begins at stage 5 prior to MEF-2. Differential expression of DNA-binding complexes is also observed with another AT-rich DNA sequence (CArG box) as probe, but the binding pattern with the ubiquitous TATA-binding proteins remains unchanged during the same developmental period. Thus, the cardiogenic commitment and differentiation of the precardiac mesoderm, as exemplified by the appearance of cardiac MEF-2, MLC2, and alpha-actin gene products, occur earlier than previously thought and appear to be closely linked. The onset of skeletal myogenic program follows that of the cardiogenic program with the appearance of skeletal MLC2 at stage 8. We also observed that mRNA for the MEF-2 family of proteins appears as early as stage 2 and that for CMD-1, the chicken counterpart of MyoD, appears at stage 5. The temporal separation of activation of cardiac and skeletal MLC2 genes, which appears immediately after the respective fate assignments, and those of cardiac MEF-2 and CMD-1, which occur before, are consistent with the established appearance of the myogenic programs and with the acquisition pattern of the two tissue-specific morphological characteristics in the early embryo. The preferential appearance of BBF-1 activity in precardiac moesderm, relative to that of MEF-2, indicates that these two protein factors are distinct members of the MEF-2 family and provides a compelling argument in support of the potential role of BBF-1 as a regulator of the cardiogenic cell lineage determination, while cardiac MEF-2 might be involved in maintenance of the cardiac differentiative state.

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24

Goswami, S., P. Qasba, S. Ghatpande, S. Carleton, A. K. Deshpande, M. Baig y M. A. Siddiqui. "Differential expression of the myocyte enhancer factor 2 family of transcription factors in development: the cardiac factor BBF-1 is an early marker for cardiogenesis." Molecular and Cellular Biology 14, n.º 8 (agosto de 1994): 5130–38. http://dx.doi.org/10.1128/mcb.14.8.5130.

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In the present study, we have used single chicken blastoderms of defined early developmental stages, beginning with the prestreak stage, stage 1 (V. Hamburger and H. L. Hamilton, J. Morphol. 88:49-92, 1951), to analyze the onset of cardiac myogenesis by monitoring the appearance of selected cardiac muscle tissue-specific gene transcripts and the functional expression of the myocyte enhancer factor 2 (MEF-2) proteins. Using gene-specific oligonucleotide primers in reverse transcriptase PCR assay, we have demonstrated that the cardiac myosin light-chain 2 (MLC2) and alpha-actin gene transcripts appear as early as stage 5, i.e., immediately after the cardiogenic fate assignment at stage 4. Consistent with this observation is the developmental expression pattern of DNA-binding activity of BBF-1, a cardiac muscle-specific member of the MEF-2 protein family, which also begins at stage 5 prior to MEF-2. Differential expression of DNA-binding complexes is also observed with another AT-rich DNA sequence (CArG box) as probe, but the binding pattern with the ubiquitous TATA-binding proteins remains unchanged during the same developmental period. Thus, the cardiogenic commitment and differentiation of the precardiac mesoderm, as exemplified by the appearance of cardiac MEF-2, MLC2, and alpha-actin gene products, occur earlier than previously thought and appear to be closely linked. The onset of skeletal myogenic program follows that of the cardiogenic program with the appearance of skeletal MLC2 at stage 8. We also observed that mRNA for the MEF-2 family of proteins appears as early as stage 2 and that for CMD-1, the chicken counterpart of MyoD, appears at stage 5. The temporal separation of activation of cardiac and skeletal MLC2 genes, which appears immediately after the respective fate assignments, and those of cardiac MEF-2 and CMD-1, which occur before, are consistent with the established appearance of the myogenic programs and with the acquisition pattern of the two tissue-specific morphological characteristics in the early embryo. The preferential appearance of BBF-1 activity in precardiac moesderm, relative to that of MEF-2, indicates that these two protein factors are distinct members of the MEF-2 family and provides a compelling argument in support of the potential role of BBF-1 as a regulator of the cardiogenic cell lineage determination, while cardiac MEF-2 might be involved in maintenance of the cardiac differentiative state.

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25

Liu, Yan, Cyrus V. Hedvat, Shifeng Mao, Xin-Hua Zhu, Jinjuan Yao, Hoang Nguyen, Andrew Koff y Stephen D. Nimer. "The ETS Protein MEF Is Regulated by Phosphorylation-Dependent Proteolysis via the Protein-Ubiquitin Ligase SCFSkp2". Molecular and Cellular Biology 26, n.º 8 (15 de abril de 2006): 3114–23. http://dx.doi.org/10.1128/mcb.26.8.3114-3123.2006.

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ABSTRACT MEF is an ETS-related transcription factor with strong transcriptional activating activity that affects hematopoietic stem cell behavior and is required for normal NK cell and NK T-cell development. The MEF (also known as ELF4) gene is repressed by several leukemia-associated fusion transcription factor proteins (PML-retinoic acid receptor α and AML1-ETO), but it is also activated by retroviral insertion in several cancer models. We have previously shown that cyclin A-dependent phosphorylation of MEF largely restricts its activity to the G1 phase of the cell cycle; we now show that MEF is a short-lived protein whose expression level also peaks during late G1 phase. Mutagenesis studies show that the rapid turnover of MEF in S phase is dependent on the specific phosphorylation of threonine 643 and serine 648 at the C terminus of MEF by cdk2 and on the Skp1/Cul1/F-box (SCF) E3 ubiquitin ligase complex SCFSkp2, which targets MEF for ubiquitination and proteolysis. Overexpression of MEF drives cells through the G1/S transition, thereby promoting cell proliferation. The tight regulation of MEF levels during the cell cycle contributes to its effects on regulating cell cycle entry and cell proliferation.

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26

Zhu, H., V. T. Nguyen, A. B. Brown, A. Pourhosseini, A. V. Garcia, M. van Bilsen y K. R. Chien. "A novel, tissue-restricted zinc finger protein (HF-1b) binds to the cardiac regulatory element (HF-1b/MEF-2) in the rat myosin light-chain 2 gene". Molecular and Cellular Biology 13, n.º 7 (julio de 1993): 4432–44. http://dx.doi.org/10.1128/mcb.13.7.4432-4444.1993.

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The AT-rich element MEF-2 plays an important role in the maintenance of the muscle-specific expression of a number of cardiac and skeletal muscle genes. In the MLC-2 gene, an AT-rich element (HF-1b) which contains a consensus MEF-2 site is required for cardiac tissue-specific expression. The present study reports the isolation and characterization of a cDNA which encodes a novel C2H2 zinc finger (HF-1b) that binds in a sequence-specific manner to the HF-1b/MEF-2 site in the MLC-2 promoter. A number of independent criteria suggest that this HF-1b zinc finger protein is a component of the endogenous HF-1b/MEF-2 binding activity in cardiac muscle cells and that it can serve as a transcriptional activator of the MLC-2 promoter in transient assays. These studies suggest that, in addition to the previously reported RSRF proteins, structurally divergent transcriptional factors can bind to MEF-2-like sites in muscle promoters. These results underscore the complexity of the regulation of the muscle gene program via these AT-rich elements in cardiac and skeletal muscle.

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27

Zhu, H., V. T. Nguyen, A. B. Brown, A. Pourhosseini, A. V. Garcia, M. van Bilsen y K. R. Chien. "A novel, tissue-restricted zinc finger protein (HF-1b) binds to the cardiac regulatory element (HF-1b/MEF-2) in the rat myosin light-chain 2 gene." Molecular and Cellular Biology 13, n.º 7 (julio de 1993): 4432–44. http://dx.doi.org/10.1128/mcb.13.7.4432.

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The AT-rich element MEF-2 plays an important role in the maintenance of the muscle-specific expression of a number of cardiac and skeletal muscle genes. In the MLC-2 gene, an AT-rich element (HF-1b) which contains a consensus MEF-2 site is required for cardiac tissue-specific expression. The present study reports the isolation and characterization of a cDNA which encodes a novel C2H2 zinc finger (HF-1b) that binds in a sequence-specific manner to the HF-1b/MEF-2 site in the MLC-2 promoter. A number of independent criteria suggest that this HF-1b zinc finger protein is a component of the endogenous HF-1b/MEF-2 binding activity in cardiac muscle cells and that it can serve as a transcriptional activator of the MLC-2 promoter in transient assays. These studies suggest that, in addition to the previously reported RSRF proteins, structurally divergent transcriptional factors can bind to MEF-2-like sites in muscle promoters. These results underscore the complexity of the regulation of the muscle gene program via these AT-rich elements in cardiac and skeletal muscle.

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28

Madugula, Kiran Kumar, Catherine DeMarino, Amanda Panfil, Alex Dobzanki, Rashida Ginwala, Zafar Khan, Fatah Kashanchi et al. "Regulation and perturbation of Myocyte enhancer factor-2 (MEF-2) activity in Adult T-cell leukemia/lymphoma". Journal of Immunology 202, n.º 1_Supplement (1 de mayo de 2019): 75.16. http://dx.doi.org/10.4049/jimmunol.202.supp.75.16.

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Abstract HTLV-1 is a complex human retrovirus, an etiologic agent in causing malignant and intractable T-cell neoplasia. About 5% of the infected population would progress to acquiring a more aggressive form of non-Hodgkin’s lymphoma (NHL), termed as Adult T-cell leukemia/Lymphoma (ATLL). MEF-2 transcription factors are a family of genes that are involved in distinct functions in various tissues and isoforms of MEF-2 are 2A, 2B, 2C, 2D in mammals whose mutations are implicated in various cancers. Earlier studies from our lab delineated the role of MEF-2A in increased viral gene expression and inhibition of MEF-2A lead to the reduction in HTLV-1 viral replication and associated T-cell transformation. Presently, we have adopted to novel cyto-analytical techniques to quantitate gene transcripts and protein expression patterns at a single cell level for all the MEF-2 isoforms in different cell systems representing productive viral infection and/or ATLL. These studies revealed post-translationally modified, overexpression of MEF-2C and downregulated expression of MEF-2B which are known to be oncogene and tumor suppressor respectively. Similar results were obtained with a unique and specific HDAC-IIa inhibitor namely MC1568, which led to a dose-dependent cancer cell (but not normal) death in vitro while inhibiting viral proteins (Tax and HBZ) expression in vivo. In addition, exposure of HTLV-1-infected cells to MC1568 resulted in the activation of autophagy marker, LC3-II that is currently under investigation to a more in-depth mechanistic analysis.

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Wipke, Brian T., Robert Hoepner, Katrin Strassburger-Krogias, Ankur M. Thomas, Davide Gianni, Suzanne Szak, Melanie S. Brennan et al. "Different Fumaric Acid Esters Elicit Distinct Pharmacologic Responses". Neurology - Neuroimmunology Neuroinflammation 8, n.º 2 (19 de enero de 2021): e950. http://dx.doi.org/10.1212/nxi.0000000000000950.

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ObjectiveTo test the hypothesis that dimethyl fumarate (DMF, Tecfidera) elicits different biological changes from DMF combined with monoethyl fumarate (MEF) (Fumaderm, a psoriasis therapy), we investigated DMF and MEF in rodents and cynomolgus monkeys. Possible translatability of findings was explored with lymphocyte counts from a retrospective cohort of patients with MS.MethodsIn rodents, we evaluated pharmacokinetic and pharmacodynamic effects induced by DMF and MEF monotherapies or in combination (DMF/MEF). Clinical implications were investigated in a retrospective, observational analysis of patients with MS treated with DMF/MEF (n = 36).ResultsIn rodents and cynomolgus monkeys, monomethyl fumarate (MMF, the primary metabolite of DMF) exhibited higher brain penetration, whereas MEF was preferentially partitioned into the kidney. In mice, transcriptional profiling for DMF and MEF alone identified both common and distinct pharmacodynamic responses, with almost no overlap between DMF- and MEF-induced differentially expressed gene profiles in immune tissues. The nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated oxidative stress response pathway was exclusively regulated by DMF, whereas apoptosis pathways were activated by MEF. DMF/MEF treatment demonstrated that DMF and MEF functionally interact to modify DMF- and MEF-specific responses in unpredictable ways. In patients with MS, DMF/MEF treatment led to early and pronounced suppression of lymphocytes, predominantly CD8+ T cells. In a multivariate regression analysis, the absolute lymphocyte count (ALC) was associated with age at therapy start, baseline ALC, and DMF/MEF dosage but not with previous immunosuppressive medication and sex. Furthermore, the ALC increased in a small cohort of patients with MS (n = 6/7) after switching from DMF/MEF to DMF monotherapy.ConclusionsFumaric acid esters exhibit different biodistribution and may elicit different biological responses; furthermore, pharmacodynamic effects of combinations differ unpredictably from monotherapy. The strong potential to induce lymphopenia in patients with MS may be a result of activation of apoptosis pathways by MEF compared with DMF.

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30

Xu, Xiaoping, Lin Cai, Meng Xiao, Fanrong Kong, Shahin Oftadeh, Fei Zhou y Gwendolyn L. Gilbert. "Distribution of Serotypes, Genotypes, and Resistance Determinants among Macrolide-Resistant Streptococcus pneumoniae Isolates". Antimicrobial Agents and Chemotherapy 54, n.º 3 (11 de enero de 2010): 1152–59. http://dx.doi.org/10.1128/aac.01268-09.

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ABSTRACT Macrolide resistance in Streptococcus pneumoniae has emerged as an important clinical problem worldwide over the past decade. The aim of this study was to analyze the phenotypes (serotype and antibiotic susceptibility), genotypes (multilocus sequence type [MLST] and antibiotic resistance gene/transposon profiles) among the 31% (102/328) of invasive isolates from children in New South Wales, Australia, in 2005 that were resistant to erythromycin. Three serotypes—19F (47 isolates [46%]), 14 (27 isolates [26%]), and 6B (12 isolates [12%])—accounted for 86 (84%) of these 102 isolates. Seventy four (73%) isolates had the macrolide-lincosamide-streptogramin B (MLSB) resistance phenotype and carried Tn916 transposons (most commonly Tn6002); of these, 73 (99%) contained the erythromycin ribosomal methylase gene [erm(B)], 34 (47%) also carried the macrolide efflux gene [mef(E)], and 41 (55%) belonged to serotype 19F. Of 28 (27%) isolates with the M phenotype, 22 (79%) carried mef(A), including 16 (57%) belonging to serotype 14, and only six (19%) carried Tn916 transposons. Most (84%) isolates which contained mef also contained one of the msr(A) homologues, mel or msr(D); 38 of 40 (95%) isolates with mef(E) (on mega) carried mel, and of 28 (39%) isolates with mef(A), 10 (39%) carried mel and another 11(39%) carried msr(D), on Tn1207.1. Two predominant macrolide-resistant S. pneumoniae clonal clusters (CCs) were identified in this population. CC-271 contained 44% of isolates, most of which belonged to serotype 19F, had the MLSB phenotype, were multidrug resistant, and carried transposons of the Tn916 family; CC-15 contained 23% of isolates, most of which were serotype 14, had the M phenotype, and carried mef(A) on Tn1207.1. Erythromycin resistance among S. pneumoniae isolates in New South Wales is mainly due to the dissemination of multidrug-resistant S. pneumoniae strains or horizontal spread of the Tn916 family of transposons.

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Chen, Shen Liang, Dennis H. Dowhan, Brett M. Hosking y George E. O. Muscat. "The steroid receptor coactivator, GRIP-1, is necessary for MEF-2C-dependent gene expression and skeletal muscle differentiation". Genes & Development 14, n.º 10 (15 de mayo de 2000): 1209–28. http://dx.doi.org/10.1101/gad.14.10.1209.

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Nuclear receptor-mediated activation of transcription involves coactivation by cofactors collectively denoted the steroid receptor coactivators (SRCs). The process also involves the subsequent recruitment of p300/CBP and PCAF to a complex that synergistically regulates transcription and remodels the chromatin. PCAF and p300 have also been demonstrated to function as critical coactivators for the muscle-specific basic helix–loop–helix (bHLH) protein MyoD during myogenic commitment. Skeletal muscle differentiation and the activation of muscle-specific gene expression is dependent on the concerted action of another bHLH factor, myogenin, and the MADS protein, MEF-2, which function in a cooperative manner. We examined the functional role of one SRC, GRIP-1, in muscle differentiation, an ideal paradigm for the analysis of the determinative events that govern the cell's decision to divide or differentiate. We observed that the mRNA encoding GRIP-1 is expressed in proliferating myoblasts and post-mitotic differentiated myotubes, and that protein levels increase during differentiation. Exogenous/ectopic expression studies with GRIP-1 sense and antisense vectors in myogenic C2C12 cells demonstrated that this SRC is necessary for (1) induction/activation of myogenin, MEF-2, and the crucial cell cycle regulator, p21, and (2) contractile protein expression and myotube formation. Furthermore, we demonstrate that the SRC GRIP-1 coactivates MEF-2C-mediated transcription. GRIP-1 also coactivates the synergistic transactivation of E box-dependent transcription by myogenin and MEF-2C. GST-pulldowns, mammalian two-hybrid analysis, and immunoprecipitation demonstrate that the mechanism involves direct interactions between MEF-2C and GRIP-1 and is associated with the ability of the SRC to interact with the MADS domain of MEF-2C. The HLH region of myogenin mediates the direct interaction of myogenin and GRIP-1. Interestingly, interaction with myogenic factors is mediated by two regions of GRIP-1, an amino-terminal bHLH–PAS region and the carboxy-terminal region between amino acids 1158 and 1423 (which encodes an activation domain, has HAT activity, and interacts with the coactivator-associated arginine methyltransferase). This work demonstrates that GRIP-1 potentiates skeletal muscle differentiation by acting as a critical coactivator for MEF-2C-mediated transactivation and is the first study to ascribe a function to the amino-terminal bHLH–PAS region of SRCs.

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32

Jain, Pooja. "Myocyte enhancer factor-2 plays critical roles in HTLV-1 infection and transformation of CD4+ T cells associated with adult T cell leukemia (ATL) by stabilizing complex between Tax and CREB (HUM8P.335)". Journal of Immunology 192, n.º 1_Supplement (1 de mayo de 2014): 185.10. http://dx.doi.org/10.4049/jimmunol.192.supp.185.10.

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Abstract The exact molecular mechanisms regarding HTLV-1 Tax-mediated viral gene expression and CD4+ T cell transformation have yet to be fully delineated. Herein, utilizing virus infected primary CD4+ T cells and the virus-producing cell line, MT-2, we describe the role of myocyte enhancer factor-2 (MEF-2) in Tax-mediated transactivation of the LTR. Inhibition of MEF-2 expression by shRNA and its activity by HDAC9 led to reduced viral replication and HTLV-mediated T cell transformation in correlation with a heightened expression of MEF-2 in ATL patients. Mechanistically, MEF-2 was shown to be recruited to the HTLV-1 LTR followed by an assessment of MEF-2 binding site(s). A novel promoter-binding assay confirmed that MEF-2 constitutes the transcriptional complex that assembles on the LTR. Furthermore, an increase in MEF-2 expression was observed upon infection in an extent similar to CREB (the known Tax-interacting transcription factor) and HATs - p300, CBP, and p/CAF. Confocal imaging confirmed MEF-2 co-localization with Tax and these proteins were also shown to interact by co-immunoprecipitation. A number of MEF-2-integrated signaling pathways were activated during HTLV-1 infection of primary CD4+ T cells, including PI3K/Akt, NF-κB, MAPK, JAK/STAT and TGF-β possibly regulating MEF-2 activity. Overall, these studies are the first to describe the involvement and regulation of a novel transcription factor during the course of a retroviral infection and associated disease syndrome.

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33

Parmacek, M. S., H. S. Ip, F. Jung, T. Shen, J. F. Martin, A. J. Vora, E. N. Olson y J. M. Leiden. "A novel myogenic regulatory circuit controls slow/cardiac troponin C gene transcription in skeletal muscle". Molecular and Cellular Biology 14, n.º 3 (marzo de 1994): 1870–85. http://dx.doi.org/10.1128/mcb.14.3.1870-1885.1994.

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The slow/cardiac troponin C (cTnC) gene is expressed in three distinct striated muscle lineages: cardiac myocytes, embryonic fast skeletal myotubes, and adult slow skeletal myocytes. We have reported previously that cTnC gene expression in cardiac muscle is regulated by a cardiac-specific promoter/enhancer located in the 5' flanking region of the gene (bp -124 to +1). In this report, we demonstrate that the cTnC gene contains a second distinct and independent transcriptional enhancer which is located in the first intron. This second enhancer is skeletal myotube specific and is developmentally up-regulated during the differentiation of myoblasts to myotubes. This enhancer contains three functionally important nuclear protein binding sites: a CACCC box, a MEF-2 binding site, and a previously undescribed nuclear protein binding site, designated MEF-3, which is also present in a large number of skeletal muscle-specific transcriptional enhancers. Unlike most skeletal muscle-specific transcriptional regulatory elements, the cTnC enhancer does not contain a consensus binding site (CANNTG) for the basic helix-loop-helix (bHLH) family of transcription factors and does not directly bind MyoD-E12 protein complexes. Despite these findings, the cTnC enhancer can be transactivated by overexpression of the myogenic bHLH proteins, MyoD and myogenin, in C3H10T1/2 (10T1/2) cells. Electrophoretic mobility shift assays demonstrated changes in the patterns of MEF-2, CACCC, and MEF-3 DNA binding activities following the conversion of 10T1/2 cells into myoblasts and myotubes by stable transfection with a MyoD expression vector. In particular, MEF-2 binding activity was up-regulated in 10T1/2 cells stably transfected with a MyoD expression vector only after these cells fused and differentiated into skeletal myotubes. Taken together, these results demonstrated that distinct lineage-specific transcriptional regulatory elements control the expression of a single myofibrillar protein gene in fast skeletal and cardiac muscle. In addition, they show that bHLH transcription factors can indirectly transactivate the expression of some muscle-specific genes.

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34

Parmacek, M. S., H. S. Ip, F. Jung, T. Shen, J. F. Martin, A. J. Vora, E. N. Olson y J. M. Leiden. "A novel myogenic regulatory circuit controls slow/cardiac troponin C gene transcription in skeletal muscle." Molecular and Cellular Biology 14, n.º 3 (marzo de 1994): 1870–85. http://dx.doi.org/10.1128/mcb.14.3.1870.

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The slow/cardiac troponin C (cTnC) gene is expressed in three distinct striated muscle lineages: cardiac myocytes, embryonic fast skeletal myotubes, and adult slow skeletal myocytes. We have reported previously that cTnC gene expression in cardiac muscle is regulated by a cardiac-specific promoter/enhancer located in the 5' flanking region of the gene (bp -124 to +1). In this report, we demonstrate that the cTnC gene contains a second distinct and independent transcriptional enhancer which is located in the first intron. This second enhancer is skeletal myotube specific and is developmentally up-regulated during the differentiation of myoblasts to myotubes. This enhancer contains three functionally important nuclear protein binding sites: a CACCC box, a MEF-2 binding site, and a previously undescribed nuclear protein binding site, designated MEF-3, which is also present in a large number of skeletal muscle-specific transcriptional enhancers. Unlike most skeletal muscle-specific transcriptional regulatory elements, the cTnC enhancer does not contain a consensus binding site (CANNTG) for the basic helix-loop-helix (bHLH) family of transcription factors and does not directly bind MyoD-E12 protein complexes. Despite these findings, the cTnC enhancer can be transactivated by overexpression of the myogenic bHLH proteins, MyoD and myogenin, in C3H10T1/2 (10T1/2) cells. Electrophoretic mobility shift assays demonstrated changes in the patterns of MEF-2, CACCC, and MEF-3 DNA binding activities following the conversion of 10T1/2 cells into myoblasts and myotubes by stable transfection with a MyoD expression vector. In particular, MEF-2 binding activity was up-regulated in 10T1/2 cells stably transfected with a MyoD expression vector only after these cells fused and differentiated into skeletal myotubes. Taken together, these results demonstrated that distinct lineage-specific transcriptional regulatory elements control the expression of a single myofibrillar protein gene in fast skeletal and cardiac muscle. In addition, they show that bHLH transcription factors can indirectly transactivate the expression of some muscle-specific genes.

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35

Serman, Yair, Rodrigo A. Fuentealba, Consuelo Pasten, Jocelyn Rocco, Ben C. B. Ko, Flavio Carrión y Carlos E. Irarrázabal. "Emerging new role of NFAT5 in inducible nitric oxide synthase in response to hypoxia in mouse embryonic fibroblast cells". American Journal of Physiology-Cell Physiology 317, n.º 1 (1 de julio de 2019): C31—C38. http://dx.doi.org/10.1152/ajpcell.00054.2019.

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We previously described the protective role of the nuclear factor of activated T cells 5 (NFAT5) during hypoxia. Alternatively, inducible nitric oxide synthase (iNOS) is also induced by hypoxia. Some evidence indicates that NFAT5 is essential for the expression of iNOS in Toll-like receptor-stimulated macrophages and that iNOS inhibition increases NFAT5 expression in renal ischemia-reperfusion. Here we studied potential NFAT5 target genes stimulated by hypoxia in mouse embryonic fibroblast (MEF) cells. We used three types of MEF cells associated with NFAT5 gene: NFAT5 wild type (MEF-NFAT5+/+), NFAT5 knockout (MEF-NFAT5−/−), and NFAT5 dominant-negative (MEF-NFAT5Δ/Δ) cells. MEF cells were exposed to 21% or 1% O2 in a time course curve of 48 h. We found that, in MEF-NFAT5+/+ cells exposed to 1% O2, NFAT5 was upregulated and translocated into the nuclei, and its transactivation domain activity was induced, concomitant with iNOS, aquaporin 1 (AQP-1), and urea transporter 1 (UTA-1) upregulation. Interestingly, in MEF-NFAT5−/− or MEF-NFAT5Δ/Δ cells, the basal levels of iNOS and AQP-1 expression were strongly downregulated, but not for UTA-1. The upregulation of AQP-1, UTA-1, and iNOS by hypoxia was blocked in both NFAT5-mutated cells. The iNOS induction by hypoxia was recovered in MEF-NFAT5−/− MEF cells, when recombinant NFAT5 protein expression was reconstituted, but not in MEF-NFAT5Δ/Δ cells, confirming the dominant-negative effect of MEF-NFAT5Δ/Δ cells. We did not see the rescue effect on AQP-1 expression. This work provides novel and relevant information about the signaling pathway of NFAT5 during responses to oxygen depletion in mammalian cells and suggests that the expression of iNOS induced by hypoxia is dependent on NFAT5.

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36

Luna, Vicki A., Marc Heiken, Kathleen Judge, Catherine Ulep, Nicole Van Kirk, Henrique Luis, Mario Bernardo, Jose Leitao y Marilyn C. Roberts. "Distribution of mef(A) in Gram-Positive Bacteria from Healthy Portuguese Children". Antimicrobial Agents and Chemotherapy 46, n.º 8 (agosto de 2002): 2513–17. http://dx.doi.org/10.1128/aac.46.8.2513-2517.2002.

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ABSTRACT We screened 615 gram-positive isolates from 150 healthy children for the presence of the erm(A), erm(B), erm(C), erm(F), and mef(A) genes. The mef(A) genes were found in 20 (9%) of the macrolide-resistant isolates, including Enterococcus spp., Staphylococcus spp., and Streptococcus spp. Sixteen of the 19 gram-positive isolates tested carried the other seven open reading frames (ORFs) described in Tn1207.1, a genetic element carrying mef(A) recently described in Streptococcus pneumoniae. The three Staphylococcus spp. did not carry orf1 to orf3. A gram-negative Acinetobacter junii isolate also carried the other seven ORFs described in Tn1207.1. A Staphylococcus aureus isolate, a Streptococcus intermedius isolate, a Streptococcus sp. isolate, and an Enterococcus sp. isolate had their mef(A) genes completely sequenced and showed 100% identity at the DNA and amino acid levels with the mef(A) gene from S. pneumoniae.

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37

Reyes-Juárez, José Luis, Raúl Juárez-Rubí, Gabriela Rodríguez y Angel Zarain-Herzberg. "Transcriptional Analysis of the Human Cardiac Calsequestrin Gene in Cardiac and Skeletal Myocytes". Journal of Biological Chemistry 282, n.º 49 (15 de octubre de 2007): 35554–63. http://dx.doi.org/10.1074/jbc.m707788200.

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Calsequestrin is the main calcium-binding protein inside the sarcoplasmic reticulum of striated muscle. In mammals, the cardiac calsequestrin gene (casq2) mainly expresses in cardiac muscle and to a minor extent in slow-twitch skeletal muscle and it is not expressed in non-muscle tissues. This work is the first study on the transcriptional regulation of the casq2 gene in cardiac and skeletal muscle cells. The sequence of the casq2 genes proximal promoter (180 bp) of mammals and avians is highly conserved and contains one TATA box, one CArG box, one E-box, and one myocyte enhancer factor 2 (MEF-2) site. We cloned the human casq2 gene 5′-regulatory region into a luciferase reporter expression vector. By functional assays we showed that a construct containing the first 288 bp of promoter was up-regulated during myogenic differentiation of Sol8 cells and had higher transcriptional activity compared with longer constructs. In neonatal rat cardiac myocytes, the larger construct containing 3.2 kb showed the highest transcriptional activity, demonstrating that the first 288 bp are sufficient to confer muscle specificity, whereas distal sequences may act as a cardiac-specific enhancer. Electrophoretic mobility shift assay studies demonstrated that the proximal MEF-2 and CArG box sequences were capable of binding MEF-2 and serum response factor, respectively, whereas the E-box did not show binding properties. Functional studies demonstrated that site-directed mutagenesis of the proximal MEF-2 and CArG box sites significantly decreased the transcription of the gene in cardiac and skeletal muscle cells, indicating that they are important to drive cardiac and skeletal muscle-specific transcription of the casq2 gene.

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38

Cai, Y., F. Kong y G. L. Gilbert. "Three New Macrolide Efflux (mef) Gene Variants in Streptococcus agalactiae". Journal of Clinical Microbiology 45, n.º 8 (27 de junio de 2007): 2754–55. http://dx.doi.org/10.1128/jcm.00579-07.

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39

McGee, Lesley, Keith P. Klugman, Avril Wasas, Thora Capper y Adrian Brink. "Serotype 19F Multiresistant Pneumococcal Clone Harboring Two Erythromycin Resistance Determinants [erm(B) and mef(A)] in South Africa". Antimicrobial Agents and Chemotherapy 45, n.º 5 (1 de mayo de 2001): 1595–98. http://dx.doi.org/10.1128/aac.45.5.1595-1598.2001.

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ABSTRACT One hundred eighteen erythromycin-resistant Streptococcus pneumoniae (ERSP) strains (MICs of ≥0.5 μg/ml) from five laboratories serving the private sector in South Africa were analyzed for the genes encoding resistance to macrolides. Sixty-seven ERSP strains (56.8%) contained the erm(B) gene, and 15 isolates (12.7%) contained the mef(A) gene. Thirty-six isolates (30.5%) harbored both the erm(B) and mef(A) genes and were highly resistant to erythromycin and clindamycin. DNA fingerprinting by BOX-PCR and pulsed-field gel electrophoresis identified 83% of these strains as belonging to a single multiresistant serotype 19F clone.

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40

Bui, Anh Son, Dinh Chinh Duong, Thi Hong Hanh Le y Ngoc Anh Do. "Prevalence of mef(A) and erm(B) in macrolide-resistant Streptococcus pneumoniaeisolates in children with pneumonia in Nghe An (2019-2021)". Ministry of Science and Technology, Vietnam 65, n.º 2 (25 de febrero de 2023): 9–13. http://dx.doi.org/10.31276/vjst.65(2).09-13.

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The present study aimed to determine the incidence of erm(B) and mef(A) among macrolide-resistant S. pneumoniae isolated in children with pneumonia in Nghe An province (2019-2021). A total of 126 clinical pnemococcal strains isolated from unvaccinated children less than 5 years of age with pneumonia at the Nghe An Obstetrics and Pediatrics Hospital, Vietnam during the period from Nov 2019 and Dec 2021. All strains were identified using conventional microbiological method, VITEK® 2 Compact system and specific PCR. The antimicrobial resistance patterns of pnemococcal strains were determined using the VITEK® 2 Compact system. Polymerase chain reaction (PCR) assay were used to detect the macrolide resistance genes erm(B) and mef(A). Of the 126 isolates, 92.1% (116 of 126) were PCR positive for erm(B) and 57.9% (73 of 126) were PCR positive for mef(A). 120 (95.3%) had the mef(A) and/or the erm(B) gene and 54.8% of strains were both erm(B) and mef(A) positive. The findings of the current study showed high prevalence of the mef(A) and erm(B) genes among macrolide-resistant S. pneumoniae isolates in children with pneumonia in Nghe An province.

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41

Mao, Shifeng, Richard C. Frank, Jin Zhang, Yasushi Miyazaki y Stephen D. Nimer. "Functional and Physical Interactions between AML1 Proteins and an ETS Protein, MEF: Implications for the Pathogenesis of t(8;21)-Positive Leukemias". Molecular and Cellular Biology 19, n.º 5 (1 de mayo de 1999): 3635–44. http://dx.doi.org/10.1128/mcb.19.5.3635.

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ABSTRACT The AML1 and ETS families of transcription factors play critical roles in hematopoiesis; AML1, and its non-DNA-binding heterodimer partner CBFβ, are essential for the development of definitive hematopoiesis in mice, whereas the absence of certain ETS proteins creates specific defects in lymphopoiesis or myelopoiesis. The promoter activities of numerous genes expressed in hematopoietic cells are regulated by AML1 proteins or ETS proteins. MEF (for myeloid ELF-1-like factor) is a recently cloned ETS family member that, like AML1B, can strongly transactivate several of these promoters, which led us to examine whether MEF functionally or physically interacts with AML1 proteins. In this study, we demonstrate direct interactions between MEF and AML1 proteins, including the AML1/ETO fusion protein, in t(8;21)-positive acute myeloid leukemia (AML) cells. Using mutational analysis, we identified a novel ETS-interacting subdomain (EID) in the C-terminal portion of the Runt homology domain (RHD) in AML1 proteins and determined that the N-terminal region of MEF was responsible for its interaction with AML1. MEF and AML1B synergistically transactivated an interleukin 3 promoter reporter gene construct, yet the activating activity of MEF was abolished when MEF was coexpressed with AML1/ETO. The repression by AML1/ETO was independent of DNA binding but depended on its ability to interact with MEF, suggesting that AML1/ETO can repress genes not normally regulated by AML1 via protein-protein interactions. Interference with MEF function by AML1/ETO may lead to dysregulation of genes important for myeloid differentiation, thereby contributing to the pathogenesis of t(8;21) AML.

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42

Klaassen, Corné H. W. y Johan W. Mouton. "Molecular Detection of the Macrolide Efflux Gene: To Discriminate or Not To Discriminate between mef(A) and mef(E)". Antimicrobial Agents and Chemotherapy 49, n.º 4 (abril de 2005): 1271–78. http://dx.doi.org/10.1128/aac.49.4.1271-1278.2005.

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43

Zhou, M. D., S. K. Goswami, M. E. Martin y M. A. Siddiqui. "A new serum-responsive, cardiac tissue-specific transcription factor that recognizes the MEF-2 site in the myosin light chain-2 promoter". Molecular and Cellular Biology 13, n.º 2 (febrero de 1993): 1222–31. http://dx.doi.org/10.1128/mcb.13.2.1222-1231.1993.

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We have identified a serum-responsive, cardiac tissue-specific transcription factor, BBF-1, that recognizes an AT-rich sequence (element B), identical to the myocyte enhancer factor (MEF-2) target site, in the cardiac myosin light chain-2 (MLC-2) promoter. Deletion of the element B sequence alone from the cardiac MLC-2 promoter causes, as does that of the MEF-2 site from other promoters and the enhancer of skeletal muscle genes, a marked reduction of transcription. BBF-1 is distinguishable from cardiac MEF-2 on the basis of immunoprecipitation with an antibody which recognizes MEF-2 but not BBF-1. Unlike MEF-2, BBF-1 is present exclusively in nuclear extracts from cardiac muscle cells cultured in a medium containing a high concentration of serum. Removal of serum from culture medium abolishes BBF-1 activity selectively with a concomitant loss of the positive regulatory effect of element B on MLC-2 gene transcription, indicating that there is a correlation between the BBF-1 binding activity and the tissue-specific role of the element B (MEF-2 site) sequence. The loss of element B-mediated activation of transcription is reversed following the refeeding of cells with serum-containing medium. These data demonstrate that cardiac muscle cells contain two distinct protein factors, MEF-2 and BBF-1, which bind to the same target site but that, unlike MEF-2, BBF-1 is serum inducible and cardiac tissue specific. BBF-1 thus appears to be a crucial member of the MEF-2 family of proteins which will serve as an important tool in understanding the regulatory mechanism(s) underlying cardiogenic differentiation.

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44

Zhou, M. D., S. K. Goswami, M. E. Martin y M. A. Siddiqui. "A new serum-responsive, cardiac tissue-specific transcription factor that recognizes the MEF-2 site in the myosin light chain-2 promoter." Molecular and Cellular Biology 13, n.º 2 (febrero de 1993): 1222–31. http://dx.doi.org/10.1128/mcb.13.2.1222.

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We have identified a serum-responsive, cardiac tissue-specific transcription factor, BBF-1, that recognizes an AT-rich sequence (element B), identical to the myocyte enhancer factor (MEF-2) target site, in the cardiac myosin light chain-2 (MLC-2) promoter. Deletion of the element B sequence alone from the cardiac MLC-2 promoter causes, as does that of the MEF-2 site from other promoters and the enhancer of skeletal muscle genes, a marked reduction of transcription. BBF-1 is distinguishable from cardiac MEF-2 on the basis of immunoprecipitation with an antibody which recognizes MEF-2 but not BBF-1. Unlike MEF-2, BBF-1 is present exclusively in nuclear extracts from cardiac muscle cells cultured in a medium containing a high concentration of serum. Removal of serum from culture medium abolishes BBF-1 activity selectively with a concomitant loss of the positive regulatory effect of element B on MLC-2 gene transcription, indicating that there is a correlation between the BBF-1 binding activity and the tissue-specific role of the element B (MEF-2 site) sequence. The loss of element B-mediated activation of transcription is reversed following the refeeding of cells with serum-containing medium. These data demonstrate that cardiac muscle cells contain two distinct protein factors, MEF-2 and BBF-1, which bind to the same target site but that, unlike MEF-2, BBF-1 is serum inducible and cardiac tissue specific. BBF-1 thus appears to be a crucial member of the MEF-2 family of proteins which will serve as an important tool in understanding the regulatory mechanism(s) underlying cardiogenic differentiation.

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45

Del Grosso, Maria, John G. E. Northwood, David J. Farrell y Annalisa Pantosti. "The Macrolide Resistance Genes erm(B) and mef(E) Are Carried by Tn2010 in Dual-Gene Streptococcus pneumoniae Isolates Belonging to Clonal Complex CC271". Antimicrobial Agents and Chemotherapy 51, n.º 11 (20 de agosto de 2007): 4184–86. http://dx.doi.org/10.1128/aac.00598-07.

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ABSTRACT The genetic elements carrying macrolide resistance genes in Streptococcus pneumoniae isolates belonging to CC271 were investigated. The international clone Taiwan19F-14 was found to carry Tn2009, a Tn916-like transposon containing tet(M) and mef(E). The dual erm(B) mef(E) isolates carried Tn2010, which is similar to Tn2009 with the addition of a putative new transposon, the erm(B) genetic element.

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46

Liu, Yan, Shannon E. Elf, Yasuhiko Miyata, Goro Sashida, Anthony D. Deblasio, Yuhui Liu, Andrew Koff y Stephen D. Nimer. "Regulation of Hematopoietic Stem Cell Quiescence - A Novel Role for p53." Blood 110, n.º 11 (16 de noviembre de 2007): 92. http://dx.doi.org/10.1182/blood.v110.11.92.92.

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Abstract Although the p53 tumor suppressor can elicit cell-cycle arrest or apoptosis in hematopoietic cells upon DNA damage, its function during steady-state hematopoiesis is largely unknown. We demonstrated that the Ets transcription factor MEF/ELF4 regulates both HSC proliferation/self-renewal and quiescence, as Mef null mice exhibit greater numbers of hematopoietic stem cells and the Mef null HSCs are more quiescent than normal. As such, the hematopoietic compartment of Mef null mice shows significant resistance to chemotherapy and radiation (Lacorazza et al., Cancer Cell, 2006). In this study, we have investigated the mechanisms utilized by MEF/ELF4 to regulate the quiescence and self-renewal of hematopoietic stem cells, identifying p53 as a key regulator. We have recently found that Mef null mouse embryonic fibroblasts (mefs) accumulate p53 and undergo premature senescence; MEF appears to surpress the expression of p53 by directly upregulating Mdm2 (G. Sashida et al., submitted). We hypothesized that p53 may play a role in the enhanced stem cell quiescence or the increased HSC frequency seen in Mef null mice. To examine this, we generated p53−/− Mef −/− mice and compared HSC biology in the double knock out mice (p53−/− Mef −/−) vs p53 null mice, Mef null mice and wt mice. Loss of p53 decreased the fraction of Pyronin Ylow Lin-Sca-1+ cells, suggesting fewer quiescent HSCs, and staining of CD34-LSK cells for the proliferation marker Ki67 also showed enhanced HSC proliferation in the absence of p53 (with fewer quiescent cells present). These data suggest that p53 promotes quiescence in HSCs, and in the absence of p53, HSCs more readily enter the cell cycle. When we analyzed the DKO (p53−/− Mef −/−) mice, we observed that the percentage of G0 HSCs returned to normal, indicating that p53 is essential for maintaining the enhanced quiescence of MEF null HSCs. p21 is a major target gene of p53 in cells, and has been shown to play an important role in maintaining HSC quiescence. As expeceted, we found elevated levels of p21 mRNA in MEF null LSK cells and reasoned that p21 may account for their enhanced quiescence. We generated p21 −/− Mef −/− mice, which are viable, born at normal mendelian frequency and appear grossly normal. However, cell cycle analysis of HSCs obtained from p21 −/− Mef −/− mice showed that the enhanced quiescence in MEF null HSCs did not depend on p21, indicating that other p53 target genes play an important role in maintaining stem cell quiescence. We therefore utilized transcript profiling (Microarray studies and quantitative PCR analysis) to identify potential p53-regulated genes that may be differentialy expressed in LSK cells isolated from wild type, p53−/−, Mef −/−, and p53−/− Mef −/− mice. By ChiP and luciferase reporter assays, we show for the first time that Gfi-1 and Necdin are direct transcriptional targets of p53 in HSCs and both Gfi-1 and Necdin regulate the enhanced quiescence exhibited in MEF null HSCs. Taken together, our work defines a novel role for p53 in the maintenance of HSC quiescence. Furthermore, HSC quiescence and self-renewal appear to be mediated by different p53 target genes during steady state hematopoiesis.

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47

Villedieu, A., A. P. Roberts, E. Allan, H. Hussain, R. McNab, D. A. Spratt, M. Wilson y P. Mullany. "Determination of the Genetic Support for tet(W) in Oral Bacteria". Antimicrobial Agents and Chemotherapy 51, n.º 6 (19 de marzo de 2007): 2195–97. http://dx.doi.org/10.1128/aac.01587-06.

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ABSTRACT The DNA sequence flanking a tet(W) gene in an oral Rothia sp. was determined. The gene was linked to two different transposases, and these were flanked by two almost identical mef (macrolide efflux) genes. This structure was found in 4 out of 20 tet(W)-containing oral bacteria investigated.

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48

Clancy, J., F. Dib-Hajj, J. W. Petitpas y W. Yuan. "Cloning and characterization of a novel macrolide efflux gene, mreA, from Streptococcus agalactiae." Antimicrobial Agents and Chemotherapy 41, n.º 12 (diciembre de 1997): 2719–23. http://dx.doi.org/10.1128/aac.41.12.2719.

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A strain of Streptococcus agalactiae displayed resistance to 14-, 15-, and 16-membered macrolides. In PCR assays, total genomic DNA from this strain contained neither erm nor mef genes. EcoRI-digested genomic DNA from this strain was cloned into lambda Zap II to construct a library of S. agalactiae genomic DNA. A clone, pAES63, expressing resistance to erythromycin, azithromycin, and spiramycin in Escherichia coli was recovered. Deletion derivatives of pAES63 which defined a functional region on this clone that encoded resistance to 14- and 15-membered, but not 16-membered, macrolides were produced. Studies that determined the levels of incorporation of radiolabelled erythromycin into E. coli were consistent with the presence of a macrolide efflux determinant. This putative efflux determinant was distinct from the recently described Mef pump in Streptococcus pyogenes and Streptococcus pneumoniae and from the multicomponent MsrA pump in Staphylococcus aureus and coagulase-negative staphylococci. Its gene has been designated mreA (for macrolide resistance efflux).

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49

Vissing, Kristian, Jesper L. Andersen, Stephen D. R. Harridge, Claudia Sandri, Andreas Hartkopp, Michael Kjaer y Peter Schjerling. "Gene expression of myogenic factors and phenotype-specific markers in electrically stimulated muscle of paraplegics". Journal of Applied Physiology 99, n.º 1 (julio de 2005): 164–72. http://dx.doi.org/10.1152/japplphysiol.01172.2004.

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The transcription factors myogenin and MyoD have been suggested to be involved in maintaining slow and fast muscle-fiber phenotypes, respectively, in rodents. Whether this is also the case in human muscle is unknown. To test this, 4 wk of chronic, low-frequency electrical stimulation training of the tibialis anterior muscle of paraplegic subjects were used to evoke a fast-to-slow transformation in muscle phenotype. It was hypothesized that this would result from an upregulation of myogenin and a downregulation of MyoD. The training evoked the expected mRNA increase for slow fiber-specific markers myosin heavy chain I and 3-hydroxyacyl-CoA dehydrogenase A, whereas an mRNA decrease was seen for fast fiber-specific markers myosin heavy chain IIx and glycerol phosphate dehydrogenase. Although the slow fiber-specific markers citrate synthase and muscle fatty acid binding protein did not display a significant increase in mRNA, they did tend to increase. As hypothesized, myogenin mRNA was upregulated. However, contrary to the hypothesis, MyoD mRNA also increased, although later than myogenin. The mRNA levels of the other myogenic regulatory factor family members, myogenic factor 5 and myogenic regulatory factor 4, and the myocyte enhancer factor (MEF) family members, MEF-2A and MEF-2C, did not change. The results indicate that myogenin is indeed involved in the regulation of the slow oxidative phenotype in human skeletal muscle fibers, whereas MyoD appears to have a more complex regulatory function.

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Kai, Hirofumi, Ayako Uto, Akinori Hisatsune, Takahiro Chihara y Takeshi Miyata. "Gene regulation in MEF-stable transfectant of the human lung adenocarcinoma cells". Japanese Journal of Pharmacology 79 (1999): 264. http://dx.doi.org/10.1016/s0021-5198(19)35068-1.

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