Articles de revues : « Activated Transcription Factor 4 »

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Dohm, G. Lynis. « Invited Review : Regulation of skeletal muscle GLUT-4 expression by exercise ». Journal of Applied Physiology 93, n^o 2 (1 août 2002) : 782–87. http://dx.doi.org/10.1152/japplphysiol.01266.2001.

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The amount of GLUT-4 protein is a primary factor in determining the maximal rate of glucose transport into skeletal muscle. Therefore, it is important that we understand how exercise regulates GLUT-4 expression so that therapeutic strategies can be designed to increase muscle glucose disposal as a treatment for diabetes. Muscle contraction increases the rates of GLUT-4 transcription and translation. Transcriptional control likely requires at least two DNA binding proteins, myocyte enhancer factor-2 and GLUT-4 enhancer factor, which bind to the promoter. Increased GLUT-4 expression may be mediated by the enzyme AMP-activated kinase, which is activated during exercise and has been demonstrated to increase GLUT-4 transcription. Further research needs to be done to investigate whether AMP-activated kinase activates myocyte enhancer factor-2 and GLUT-4 enhancer factor to increase transcription of the GLUT-4 gene.

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Wang, Jun, Pierre Paradis, Anne Aries, Hiba Komati, Chantal Lefebvre, Hao Wang et Mona Nemer. « Convergence of Protein Kinase C and JAK-STAT Signaling on Transcription Factor GATA-4 ». Molecular and Cellular Biology 25, n^o 22 (15 novembre 2005) : 9829–44. http://dx.doi.org/10.1128/mcb.25.22.9829-9844.2005.

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ABSTRACT Angiotensin II (AII), a potent vasoactive hormone, acts on numerous organs via G-protein-coupled receptors and elicits cell-specific responses. At the level of the heart, AII stimulation alters gene transcription and leads to cardiomyocyte hypertrophy. Numerous intracellular signaling pathways are activated in this process; however, which of these directly link receptor activation to transcriptional regulation remains undefined. We used the atrial natriuretic factor (ANF) gene (NPPA) as a marker to elucidate the signaling cascades involved in AII transcriptional responses. We show that ANF transcription is activated directly by the AII type 1 receptor and precedes the development of myocyte hypertrophy. This response maps to STAT and GATA binding sites, and the two elements transcriptionally cooperate to mediate signaling through the JAK-STAT and protein kinase C (PKC)-GATA-4 pathways. PKC phosphorylation enhances GATA-4 DNA binding activity, and STAT-1 functionally and physically interacts with GATA-4 to synergistically activate AII and other growth factor-inducible promoters. Moreover, GATA factors are able to recruit STAT proteins to target promoters via GATA binding sites, which are sufficient to support synergy. Thus, STAT proteins can act as growth factor-inducible coactivators of tissue-specific transcription factors. Interactions between STAT and GATA proteins may provide a general paradigm for understanding cell specificity of cytokine and growth factor signaling.

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Malik, S., et S. K. Karathanasis. « TFIIB-directed transcriptional activation by the orphan nuclear receptor hepatocyte nuclear factor 4. » Molecular and Cellular Biology 16, n^o 4 (avril 1996) : 1824–31. http://dx.doi.org/10.1128/mcb.16.4.1824.

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The orphan nuclear receptor hepatocyte nuclear factor 4 (HNF-4) is required for development and maintenance of the liver phenotype. HNF-4 activates several hepatocyte-specific genes, including the gene encoding apolipoprotein AI (apoAI), the major protein component of plasma high-density lipoprotein. The apoAI gene is activated by HNF-4 through a nuclear receptor binding element (site A) located in its liver-specific enhancer. To decipher the mechanism whereby HNF-4 enhances apoAI gene transcription, we have reconstituted its activity in a cell-free system. Functional HNF-4 was purified to homogeneity from a bacterial expression system. In in vitro transcription assays employing nuclear extract from HeLa cells, which do not contain HNF-4, recombinant HNF-4 stimulated transcription from basal promoters linked to site A. Activation by HNF-4 did not exhibit a ligand requirement, but phosphorylation of HNF-4 in the in vitro transcription system was observed. The activation function of HNF-4 was localized to a domain displaying strong homology to the conserved AF-2 region of nuclear receptors. Dissection of the transcription cycle revealed that HNF-4 activated transcription by facilitating assembly of a preinitiation complex intermediate consisting of TBP, the TATA box-binding protein component of TFIID and TFIID, via direct physical interactions with TFIIB. However, recruitment of TFIIB by HNF-4 was not sufficient for activation, since HNF-4 deletion derivatives lacking AF-2 bound TFIIB. On the basis of these results, HNF-4 appears to activate transcription at two distinct levels. The first step involves AF-2-independent recruitment of TFIIB to the promoter complex; the second step is AF-2 dependent and entails entry of preinitiation complex components acting downstream of TFIIB.

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Zheng, Donghai, Paul S. MacLean, Steven C. Pohnert, John B. Knight, Ann Louise Olson, William W. Winder et G. Lynis Dohm. « Regulation of muscle GLUT-4 transcription by AMP-activated protein kinase ». Journal of Applied Physiology 91, n^o 3 (1 septembre 2001) : 1073–83. http://dx.doi.org/10.1152/jappl.2001.91.3.1073.

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Skeletal muscle GLUT-4 transcription in response to treatment with 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), a known activator of AMP-activated protein kinase (AMPK), was studied in rats and mice. The increase in GLUT-4 mRNA levels in response to a single subcutaneous injection of AICAR, peaked at 13 h in white and red quadriceps muscles but not in the soleus muscle. The mRNA level of chloramphenicol acyltransferase reporter gene which is driven by 1,154 or 895 bp of the human GLUT-4 proximal promoter was increased in AICAR-treated transgenic mice, demonstrating the transcriptional upregulation of the GLUT-4 gene by AICAR. However, this induction of transcription was not apparent with 730 bp of the promoter. In addition, nuclear extracts from AICAR-treated mice bound to the consensus sequence of myocyte enhancer factor-2 (from −473 to −464) to a greater extent than from saline-injected mice. Thus AMP-activated protein kinase activation by AICAR increases GLUT-4 transcription by a mechanism that requires response elements within 895 bp of human GLUT-4 proximal promoter and that may be cooperatively mediated by myocyte enhancer factor-2.

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Rengarajan, Jyothi, Kerri A. Mowen, Kathryn D. McBride, Erica D. Smith, Harinder Singh et Laurie H. Glimcher. « Interferon Regulatory Factor 4 (IRF4) Interacts with NFATc2 to Modulate Interleukin 4 Gene Expression ». Journal of Experimental Medicine 195, n^o 8 (8 avril 2002) : 1003–12. http://dx.doi.org/10.1084/jem.20011128.

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Proteins of the nuclear factor of activated T cells (NFAT) family of transcription factors are critical for lymphocyte activation in the immune system. In particular, NFATs are important regulators of inducible IL-4 gene expression. Interferon regulatory factor 4 (IRF4) is an immune system–restricted interferon regulatory factor that is required for lymphocyte activation, but its molecular functions in the T lineage remain to be elucidated. We demonstrate that IRF4 potently synergizes with NFATc2 to specifically enhance NFATc2-driven transcriptional activation of the IL-4 promoter. This function is dependent on the physical interaction of IRF4 with NFATc2. IRF4 synergizes with NFATc2 and the IL-4–inducing transcription factor, c-maf, to augment IL-4 promoter activity as well as to elicit significant levels of endogenous IL-4 production. Furthermore, naïve T helper cells from mice lacking IRF4 are compromised severely for the production of IL-4 and other Th2 cytokines. The identification of IRF4 as a partner for NFATc2 in IL-4 gene regulation provides an important molecular function for IRF4 in T helper cell differentiation.

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Moon, Jong-Seok, Hee Eun Kim, Eunjin Koh, Se Ho Park, Won-Ji Jin, Byeong-Woo Park, Sahng Wook Park et Kyung-Sup Kim. « Krüppel-like Factor 4 (KLF4) Activates the Transcription of the Gene for the Platelet Isoform of Phosphofructokinase (PFKP) in Breast Cancer ». Journal of Biological Chemistry 286, n^o 27 (17 mai 2011) : 23808–16. http://dx.doi.org/10.1074/jbc.m111.236737.

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Krüppel-like factor 4 (KLF4) is a transcription factor that plays an important role in cell differentiation, proliferation, and survival, especially in the context of cancers. This study revealed that KLF4 activates glycolytic metabolism in breast cancer cells by up-regulating the platelet isoform of phosphofructokinase (PFKP). KLF4 activated the transcription of the PFKP gene by directly binding to the PFKP promoter. Whereas glucose uptake and lactate production were inhibited by the knockdown of KLF4, they were activated by the overexpression of KLF4. Unlike PFKP, the expressions of the other isoforms of phosphofructokinase and glycolytic genes were unaffected by KLF4. The human breast cancer tissues showed a close correlation between KLF4 and PFKP expression. This study also showed that PFKP plays a critical role in cell proliferation in breast cancer cells. In conclusion, it is suggested that KLF4 plays a role in maintenance of high glycolytic metabolism by transcriptional activation of the PFKP gene in breast cancer cells.

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Georas, Steve N., John E. Cumberland, Thomas F. Burke, Rongbing Chen, Ulrike Schindler et Vincenzo Casolaro. « Stat6 Inhibits Human Interleukin-4 Promoter Activity in T Cells ». Blood 92, n^o 12 (15 décembre 1998) : 4529–38. http://dx.doi.org/10.1182/blood.v92.12.4529.

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Abstract The differentiation of naive T-helper (Th) cells into cytokine-secreting effector Th cells requires exposure to multiple signals, including exogenous cytokines. Interleukin-4 (IL-4) plays a major role in this process by promoting the differentiation of IL-4–secreting Th2 cells. In Th2 cells, IL-4 gene expression is tightly controlled at the level of transcription by the coordinated binding of multiple transcription factors to regulatory elements in the proximal promoter region. Nuclear factor of activated T cell (NFAT) family members play a critical role in regulating IL-4 transcription and interact with up to five sequences (termed P0 through P4) in the IL-4 promoter. The molecular mechanisms by which IL-4 induces expression of the IL-4 gene are not known, although the IL-4–activated transcription factor signal transducer and activator of transcription 6 (Stat6) is required for this effect. We report here that Stat6 interacts with three binding sites in the human IL-4 promoter by electrophoretic mobility shift assays. These sites overlap the P1, P2, and P4 NFAT elements. To investigate the role of Stat6 in regulating IL-4 transcription, we used Stat6-deficient Jurkat T cells with different intact IL-4 promoter constructs in cotransfection assays. We show that, whereas a multimerized response element from the germline IgE promoter was highly induced by IL-4 in Stat6-expressing Jurkat cells, the intact human IL-4 promoter was repressed under similar conditions. We conclude that the function of Stat6 is highly dependent on promoter context and that this factor promotes IL-4 gene expression in an indirect manner.

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Georas, Steve N., John E. Cumberland, Thomas F. Burke, Rongbing Chen, Ulrike Schindler et Vincenzo Casolaro. « Stat6 Inhibits Human Interleukin-4 Promoter Activity in T Cells ». Blood 92, n^o 12 (15 décembre 1998) : 4529–38. http://dx.doi.org/10.1182/blood.v92.12.4529.424k39_4529_4538.

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The differentiation of naive T-helper (Th) cells into cytokine-secreting effector Th cells requires exposure to multiple signals, including exogenous cytokines. Interleukin-4 (IL-4) plays a major role in this process by promoting the differentiation of IL-4–secreting Th2 cells. In Th2 cells, IL-4 gene expression is tightly controlled at the level of transcription by the coordinated binding of multiple transcription factors to regulatory elements in the proximal promoter region. Nuclear factor of activated T cell (NFAT) family members play a critical role in regulating IL-4 transcription and interact with up to five sequences (termed P0 through P4) in the IL-4 promoter. The molecular mechanisms by which IL-4 induces expression of the IL-4 gene are not known, although the IL-4–activated transcription factor signal transducer and activator of transcription 6 (Stat6) is required for this effect. We report here that Stat6 interacts with three binding sites in the human IL-4 promoter by electrophoretic mobility shift assays. These sites overlap the P1, P2, and P4 NFAT elements. To investigate the role of Stat6 in regulating IL-4 transcription, we used Stat6-deficient Jurkat T cells with different intact IL-4 promoter constructs in cotransfection assays. We show that, whereas a multimerized response element from the germline IgE promoter was highly induced by IL-4 in Stat6-expressing Jurkat cells, the intact human IL-4 promoter was repressed under similar conditions. We conclude that the function of Stat6 is highly dependent on promoter context and that this factor promotes IL-4 gene expression in an indirect manner.

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Carrozza, M. J., et N. A. DeLuca. « Interaction of the viral activator protein ICP4 with TFIID through TAF250. » Molecular and Cellular Biology 16, n^o 6 (juin 1996) : 3085–93. http://dx.doi.org/10.1128/mcb.16.6.3085.

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ICP4 of herpes simplex virus is responsible for the activation of viral transcription during infection. It also efficiently activates and represses transcription in vitro depending on the promoter context. The contacts made between ICP4 and the cellular proteins that result in activated transcription have not been identified. The inability of ICP4 to activate transcription with TATA-binding protein in place of TFIID and the requirement for an initiator element for efficient ICP-4-activated transcription suggest that coactivators, such as TBP-associated factors, are involved (B. Gu and N. DeLuca, J. Virol. 68:7953-7965, 1994). In this study we showed that ICP4 activates transcription in vitro using an immunopurified TFIID, indicating that TBP-associated factors may be a sufficient subset of coactivators for ICP4-activated transcription. Similar to results seen in vivo, the presence of the ICP4 C-terminal region (amino acids 774 to 1298) was important for activation in vitro. With epitope-tagged ICP4 molecules in immunoaffinity experiments, it was shown that the C-terminal region was also required for ICP4 to interact with TFIID present in a crude transcription factor fraction. In the same assay, ICP4 was unable to interact with the basal transcription factors, TFIIB, TFIIE, TFIIF, and TFIIH and RNA polymerase II. ICP4 could also interact with TBP, independent of the C-terminal region. However, reflective of the interaction between ICP4 and TFIID, the ICP4 C-terminal region was required for an interaction with FAF250-TBP complexes and with TAF250 alone. Therefore, the interfaces or conformation of TBP mediating the interaction between ICP4 and TBP in solution is probably masked when TBP is bound to TAF250. With a series of mutant ICP4 molecules purified from herpes simplex virus-infected cells, it was shown that ICP4 molecules that can bind DNA and interact with TAF250 could activate transcription. Taken together, these results demonstrate that ICP4 interaction with TFIID involves the TAF250 molecule and the C-terminal region of ICP4 and that this interaction is part of the mechanism by which ICP4 activates transcription.

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Lopez, Alex B., Chuanping Wang, Charlie C. Huang, Ibrahim Yaman, Yi Li, Kaushik Chakravarty, Peter F. Johnson et al. « A feedback transcriptional mechanism controls the level of the arginine/lysine transporter cat-1 during amino acid starvation ». Biochemical Journal 402, n^o 1 (25 janvier 2007) : 163–73. http://dx.doi.org/10.1042/bj20060941.

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The adaptive response to amino acid limitation in mammalian cells inhibits global protein synthesis and promotes the expression of proteins that protect cells from stress. The arginine/lysine transporter, cat-1, is induced during amino acid starvation by transcriptional and post-transcriptional mechanisms. It is shown in the present study that the transient induction of cat-1 transcription is regulated by the stress response pathway that involves phosphorylation of the translation initiation factor, eIF2 (eukaryotic initiation factor-2). This phosphorylation induces expression of the bZIP (basic leucine zipper protein) transcription factors C/EBP (CCAAT/enhancer-binding protein)-β and ATF (activating transcription factor) 4, which in turn induces ATF3. Transfection experiments in control and mutant cells, and chromatin immunoprecipitations showed that ATF4 activates, whereas ATF3 represses cat-1 transcription, via an AARE (amino acid response element), TGATGAAAC, in the first exon of the cat-1 gene, which functions both in the endogenous and in a heterologous promoter. ATF4 and C/EBPβ activated transcription when expressed in transfected cells and they bound as heterodimers to the AARE in vitro. The induction of transcription by ATF4 was inhibited by ATF3, which also bound to the AARE as a heterodimer with C/EBPβ. These results suggest that the transient increase in cat-1 transcription is due to transcriptional activation caused by ATF4 followed by transcriptional repression by ATF3 via a feedback mechanism.

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Cron, Randy Q., Susan J. Bort, Yunxia Wang, Mark W. Brunvand et David B. Lewis. « T Cell Priming Enhances IL-4 Gene Expression by Increasing Nuclear Factor of Activated T Cells ». Journal of Immunology 162, n^o 2 (15 janvier 1999) : 860–70. http://dx.doi.org/10.4049/jimmunol.162.2.860.

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Abstract The repetitive activation of T cells (priming) enhances the expression of many cytokines, such as IL-4, but not others, such as IL-2. Molecular mechanisms underlying selective expression of cytokines by T cells remain poorly understood. Here we show that priming of CD4 T cells selectively enhances IL-4 expression relative to IL-2 expression by a transcriptional mechanism involving nuclear factor of activated T cells (NFAT) proteins. As detected by in vivo footprinting, priming markedly increases the activation-dependent engagement of the P0 and P1 NFAT-binding elements of the IL-4 promoter. Moreover, each proximal P element is essential for optimal IL-4 promoter activity. Activated primed CD4 T cells contain more NFAT1 and support greater NFAT-directed transcription than unprimed CD4 T cells, while activator protein 1 binding and activator protein 1-mediated transcription by both cell types is similar. Increased expression of wild-type NFAT1 substantially increases IL-4 promoter activity in unprimed CD4 T cells, suggesting NFAT1 may be limiting for IL-4 gene expression in this cell type. Furthermore, a truncated form of NFAT1 acts as a dominant-negative, reducing IL-4 promoter activity in primed CD4 T cells and confirming the importance of endogenous NFAT to increased IL-4 gene expression by effector T cells. NFAT1 appears to be the major NFAT family member responsible for the initial increased expression of IL-4 by primed CD4 T cells.

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Tomic-Canic, Marjana, Mayumi Komine, Irwin M. Freedberg et Miroslav Blumenberg. « Epidermal signal transduction and transcription factor activation in activated keratinocytes ». Journal of Dermatological Science 17, n^o 3 (juillet 1998) : 167–81. http://dx.doi.org/10.1016/s0923-1811(98)00016-4.

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Marecki, Sylvia, Michael L. Atchison et Matthew J. Fenton. « Differential Expression and Distinct Functions of IFN Regulatory Factor 4 and IFN Consensus Sequence Binding Protein in Macrophages ». Journal of Immunology 163, n^o 5 (1 septembre 1999) : 2713–22. http://dx.doi.org/10.4049/jimmunol.163.5.2713.

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Abstract IFN regulatory factor 4 (IRF4) and IFN consensus sequence binding protein (ICSBP) are highly homologous members of the growing family of IRF proteins. ICSBP expression is restricted to lymphoid and myeloid cells, whereas IRF4 expression has been reported to be lymphoid-restricted. We present evidence that primary murine and human macrophages express IRF4, thereby extending its range of expression to myeloid cells. Here, we provide a comparative analysis of IRF4 and ICSBP expression and function in distinct cell types. These IRF proteins can form specific complexes with the Ets-like protein PU.1, and can activate transcription via binding to PU.1/IRF composite sequences. EMSA analysis revealed that murine macrophages contained both IRF4/PU.1 and ICSBP/PU.1 complexes, analogous to B cells. Over-expression of ICSBP in these macrophages activated transcription of a PU.1/IRF-dependent promoter, whereas over-expression of IRF4 had no effect on this promoter. In contrast, over-expression of either IRF4 or ICSBP in both macrophages and NIH-3T3 fibroblasts suppressed transcription of the PU.1-independent H-2Ld MHC class I promoter. In NIH-3T3 fibroblasts, IRF4 and ICSBP also synergized with exogenous PU.1 to activate transcription of a PU.1/IRF-dependent promoter. Furthermore, both IRF4 and ICSBP activated transcription of the IL-1β promoter in both cell types. While this promoter is PU.1-dependent, it lacks any known PU.1/IRF composite binding sites. Synergistic activation of the IL-1β promoter by these IRF proteins and PU.1 was found to require PU.1 serine 148. Together, these data demonstrate that IRF4 and ICSBP are dichotomous regulators of transcription in macrophages.

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LaFramboise, W. A., R. C. Jayaraman, K. L. Bombach, D. P. Ankrapp, J. M. Krill-Burger, C. M. Sciulli, P. Petrosko et R. W. Wiseman. « Acute molecular response of mouse hindlimb muscles to chronic stimulation ». American Journal of Physiology-Cell Physiology 297, n^o 3 (septembre 2009) : C556—C570. http://dx.doi.org/10.1152/ajpcell.00046.2009.

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Stimulation of the mouse hindlimb via the sciatic nerve was performed for a 4-h period to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 ± 0.1 g/g body wt) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon study completion. An immediate-early growth response was present in the extensor digitorum longus (EDL) muscle (FOS, JUN, activating transcription factor 3, and musculoaponeurotic fibrosarcoma oncogene) with a similar but attenuated pattern in the soleus muscle. Transcript profiles showed decreased fast fiber-specific mRNA (myosin heavy chains 2A and 2B, fast troponins T3and I, α-tropomyosin, muscle creatine kinase, and parvalbumin) and increased slow transcripts (myosin heavy chain-1β/slow, troponin C slow, and tropomyosin 3y) in the EDL versus soleus muscles. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration in stimulated versus control muscles, whereas ultrastructural analysis showed no evidence of myofiber damage after stimulation. Multiple fiber type-specific transcription factors (tea domain family member 1, nuclear factor of activated T cells 1, peroxisome proliferator-activated receptor-γ coactivator-1α and -β, circadian locomotor output cycles kaput, and hypoxia-inducible factor-1α) increased in the EDL along with transcription factors characteristic of embryogenesis (Kruppel-like factor 4; SRY box containing 17; transcription factor 15; PBX/knotted 1 homeobox 1; and embryonic lethal, abnormal vision). No established in vivo satellite cell markers or genes activated in our parallel experiments of satellite cell proliferation in vitro (cyclins A2, B2, C, and E1and MyoD) were differentially increased in the stimulated muscles. These results indicated that the molecular onset of fast to slow phenotype conversion occurred in the EDL within 4 h of stimulation without injury or satellite cell recruitment. This conversion was associated with the expression of phenotype-specific transcription factors from resident fiber myonuclei, including the activation of nascent developmental transcriptional programs.

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Nylén, Carolina, Wataru Aoi, Ahmed M. Abdelmoez, David G. Lassiter, Leonidas S. Lundell, Harriet Wallberg-Henriksson, Erik Näslund, Nicolas J. Pillon et Anna Krook. « IL6 and LIF mRNA expression in skeletal muscle is regulated by AMPK and the transcription factors NFYC, ZBTB14, and SP1 ». American Journal of Physiology-Endocrinology and Metabolism 315, n^o 5 (1 novembre 2018) : E995—E1004. http://dx.doi.org/10.1152/ajpendo.00398.2017.

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Adenosine monophosphate-activated protein kinase (AMPK) controls glucose and lipid metabolism and modulates inflammatory responses to maintain metabolic and inflammatory homeostasis during low cellular energy levels. The AMPK activator 5-aminoimidazole-4-carboxamide-1-β-4-ribofuranoside (AICAR) interferes with inflammatory pathways in skeletal muscle, but the mechanisms are undefined. We hypothesized that AMPK activation reduces cytokine mRNA levels by blocking transcription through one or several transcription factors. Three skeletal muscle models were used to study AMPK effects on cytokine mRNA: human skeletal muscle strips obtained from healthy men incubated in vitro, primary human muscle cells, and rat L6 cells. In all three skeletal muscle systems, AICAR acutely reduced cytokine mRNA levels. In L6 myotubes treated with the transcriptional blocker actinomycin D, AICAR addition did not further reduce Il6 or leukemia inhibitory factor ( Lif) mRNA, suggesting that AICAR modulates cytokine expression through regulating transcription rather than mRNA stability. A cross-species bioinformatic approach identified novel transcription factors that may regulate LIF and IL6 mRNA. The involvement of these transcription factors was studied after targeted gene-silencing by siRNA. siRNA silencing of the transcription factors nuclear transcription factor Y subunit c ( Nfyc), specificity protein 1 ( Sp1), and zinc finger and BTB domain containing 14 ( Zbtb14), or AMPK α1/α2 subunits, increased constitutive levels of Il6 and Lif. Our results identify novel candidates in the regulation of skeletal muscle cytokine expression and identify AMPK, Nfyc, Sp1, and Zbtb14 as novel regulators of immunometabolic signals from skeletal muscle.

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Kiani, Alexander, Francisco J. Garcı́a-Cózar, Ivonne Habermann, Stefanie Laforsch, Toni Aebischer, Gerhard Ehninger et Anjana Rao. « Regulation of interferon-γ gene expression by nuclear factor of activated T cells ». Blood 98, n^o 5 (1 septembre 2001) : 1480–88. http://dx.doi.org/10.1182/blood.v98.5.1480.

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Transcription factors of the nuclear factor of activated T cells (NFAT) family are thought to regulate the expression of a variety of inducible genes such as interleukin-2 (IL-2), IL-4, and tumor necrosis factor-α. However, it remains unresolved whether NFAT proteins play a role in regulating transcription of the interferon- γ (IFN-γ) gene. Here it is shown that the transcription factor NFAT1 (NFATc2) is a major regulator of IFN-γ production in vivo. Compared with T cells expressing NFAT1, T cells lacking NFAT1 display a substantial IL-4–independent defect in expression of IFN-γ mRNA and protein. Reduced IFN-γ production by NFAT1−/−× IL-4−/− T cells is observed after primary in vitro stimulation of naive CD4+ T cells, is conserved through at least 2 rounds of T-helper cell differentiation, and occurs by a cell-intrinsic mechanism that does not depend on overexpression of the Th2-specific factors GATA-3 and c-Maf. Concomitantly, NFAT1−/−× IL-4−/− mice show increased susceptibility to infection with the intracellular parasiteLeishmania major. Moreover, IFN-γ production in a murine T-cell clone is sensitive to the selective peptide inhibitor of NFAT, VIVIT. These results suggest that IFN-γ production by T cells is regulated by NFAT1, most likely at the level of gene transcription.

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Qi, Xiaopeng, Jun Nishida, Lee Chaves, Keitaro Ohmori et Hua Huang. « CCAAT/Enhancer-binding Protein α (C/EBPα) Is Critical for Interleukin-4 Expression in Response to FcϵRI Receptor Cross-linking ». Journal of Biological Chemistry 286, n^o 18 (21 mars 2011) : 16063–73. http://dx.doi.org/10.1074/jbc.m110.213389.

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Basophils mediate many of their biological functions by producing IL-4. However, it is unknown how the Il4 gene is regulated in basophils. Here, we report that CCAAT/enhancer-binding protein α (C/EBPα), a major myeloid transcription factor, was highly expressed in basophils. We show that C/EBPα selectively activated Il4 promoter-luciferase reporter gene transcription in response to IgE cross-linking, but C/EBPα did not activate other known Th2 or mast cell enhancers. We found that the PI3K pathway and calcineurin were essential in C/EBPα-driven Il4 promoter-luciferase gene transcription. Our mutation analyses revealed that C/EBPα drove Il4 promoter-luciferase activity depending on its DNA binding domain. Mutation of the C/EBPα-binding site in the Il4 promoter region abolished C/EBPα-driven Il4 promoter-luciferase activity. Our results further showed that a mutation in nuclear factor of activated T cells (NFAT)-binding sites in the Il4 promoter also negated C/EBPα-driven Il4 promoter-luciferase activity. Our study demonstrates that C/EBPα, in cooperation with NFAT, directly regulates Il4 gene transcription.

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Han, Songyan, Jun Lu, Yu Zhang, Cao Cheng, Liping Han, Xiuli Wang, Lin Li, Chunyan Liu et Baiqu Huang. « Recruitment of histone deacetylase 4 by transcription factors represses interleukin-5 transcription ». Biochemical Journal 400, n^o 3 (28 novembre 2006) : 439–48. http://dx.doi.org/10.1042/bj20061085.

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The critical role of IL-5 (interleukin-5) in eosinophilic inflammation implicates it as a therapeutic target for allergic diseases. The aim of the present study was to elucidate the molecular basis for the involvement of reversible histone acetylation in IL-5 transcriptional regulation. We provide evidence that HDAC4 (histone deacetylase 4) and p300, a known HAT (histone acetyltransferase), reversibly controlled the activity of the IL-5 promoter in vivo and in vitro, with a concurrent alteration of histone H3 acetylation status at the promoter regions. The nucleo-cytoplasmic shuttling of HDAC4 was shown to play an important role in the suppressive function of HDAC4 in IL-5 gene expression. Point mutation and reporter ChIP (chromatin immunoprecipitation) studies determined that the four transcription factors binding on the IL-5 promoter, i.e. C/EBPβ (CAAT/enhancer-binding protein β), GATA3 (GATA binding protein 3), NFAT (nuclear factor of activated T cells) and YY1 (Yin and Yang 1), were essential for the recruitment of HDAC4. Consistent with these observations, HDAC4 was found to form protein complexes with GATA3 and YY1, and to co-exist in the nuclei with GATA3. We propose that the unique regulatory mechanism of IL-5 gene transcription involves the reversible histone modification catalysed by HDAC4 and p300, which are recruited by the transcription factors. The dynamic balance in IL-5 transcriptional regulation is achieved through interactions among HATs/HDACs, histones and transcription factors. These data contribute to understanding the molecular mechanisms of IL-5 regulation, which is crucial to the development of new therapeutic strategies for IL-5-related allergic diseases.

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Tang, Hong, et Alan McLachlan. « Avian and Mammalian Hepadnaviruses Have Distinct Transcription Factor Requirements for Viral Replication ». Journal of Virology 76, n^o 15 (1 août 2002) : 7468–72. http://dx.doi.org/10.1128/jvi.76.15.7468-7472.2002.

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ABSTRACT Hepadnavirus replication occurs in hepatocytes in vivo and in hepatoma cell lines in cell culture. Hepatitis B virus (HBV) replication can occur in nonhepatoma cells when pregenomic RNA synthesis from viral DNA is activated by the expression of the nuclear hormone receptors hepatocyte nuclear factor 4 (HNF4) and the retinoid X receptor α (RXRα) plus peroxisome proliferator-activated receptor α (PPARα) heterodimer. Nuclear hormone receptor-dependent HBV replication is inhibited by hepatocyte nuclear factor 3 (HNF3). In contrast, HNF3 and HNF4 support duck hepatitis B virus (DHBV) replication in nonhepatoma cells, whereas the RXRα-PPARα heterodimer inhibits HNF4-dependent DHBV replication. HNF3 and HNF4 synergistically activate DHBV pregenomic RNA synthesis and viral replication. The conditions that support HBV or DHBV replication in nonhepatoma cells are not able to support woodchuck hepatitis virus replication. These observations indicate that avian and mammalian hepadnaviruses have distinct transcription factor requirements for viral replication.

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Ivashkiv, L. B., E. M. Schmitt et A. Castro. « Inhibition of transcription factor Stat1 activity in mononuclear cell cultures and T cells by the cyclic AMP signaling pathway. » Journal of Immunology 157, n^o 4 (15 août 1996) : 1415–21. http://dx.doi.org/10.4049/jimmunol.157.4.1415.

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Abstract Activation of T cells results in a cascade of gene activation and subsequent proliferation and differentiation into effector phenotypes. The regulation of transcription factors belonging to the signal transducer and activator of transcription (STAT) family was analyzed in PHA-activated mononuclear cells and in purified T cells activated by cross-linking cell surface CD3. Cell activation resulted in a delayed induction of STAT DNA-binding activity, which was sustained for several days, was composed predominantly of Stat1 and Stat3, and was blocked by cycloheximide and actinomycin D. Increased Stat1 and Stat3 mRNA and protein levels were detected, respectively 4 and 24 h after activation. Stimulation of the cAMP signal transduction pathway, which skews cytokine production toward a Th2 pattern, resulted in the preferential suppression of Stat1 activity. cAMP inhibited the induction of expression of IL-2 receptor components, but did not inhibit IL-4 receptor alpha-chain and CD69 expression or the induction of activator protein 1 transcription factors. cAMP signaling inhibited Stat1 at several different levels, including suppression of DNA binding and down-regulation of Stat1 protein and mRNA levels. Our results demonstrate the regulation of STAT activity by a signaling pathway that regulates the T cell functional phenotype and is distinct from the cytokine-activated Janus kinase-STAT signaling pathway.

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Mimura, Junsei, Atsushi Inose-Maruyama, Shusuke Taniuchi, Kunio Kosaka, Hidemi Yoshida, Hiromi Yamazaki, Shuya Kasai et al. « Concomitant Nrf2- and ATF4-activation by Carnosic Acid Cooperatively Induces Expression of Cytoprotective Genes ». International Journal of Molecular Sciences 20, n^o 7 (5 avril 2019) : 1706. http://dx.doi.org/10.3390/ijms20071706.

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: Carnosic acid (CA) is a phytochemical found in some dietary herbs, such as Rosmarinus officinalis L., and possesses antioxidative and anti-microbial properties. We previously demonstrated that CA functions as an activator of nuclear factor, erythroid 2 (NF-E2)-related factor 2 (Nrf2), an oxidative stress-responsive transcription factor in human and rodent cells. CA enhances the expression of nerve growth factor (NGF) and antioxidant genes, such as HO-1 in an Nrf2-dependent manner in U373MG human astrocytoma cells. However, CA also induces NGF gene expression in an Nrf2-independent manner, since 50 μM of CA administration showed striking NGF gene induction compared with the classical Nrf2 inducer tert-butylhydroquinone (tBHQ) in U373MG cells. By comparative transcriptome analysis, we found that CA activates activating transcription factor 4 (ATF4) in addition to Nrf2 at high doses. CA activated ATF4 in phospho-eIF2α- and heme-regulated inhibitor kinase (HRI)-dependent manners, indicating that CA activates ATF4 through the integrated stress response (ISR) pathway. Furthermore, CA activated Nrf2 and ATF4 cooperatively enhanced the expression of NGF and many antioxidant genes while acting independently to certain client genes. Taken together, these results represent a novel mechanism of CA-mediated gene regulation evoked by Nrf2 and ATF4 cooperation.

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Dokter, WH, MT Esselink, MR Halie et E. Vellenga. « Interleukin-4 inhibits the lipopolysaccharide-induced expression of c- jun and c-fos messenger RNA and activator protein-1 binding activity in human monocytes ». Blood 81, n^o 2 (15 janvier 1993) : 337–43. http://dx.doi.org/10.1182/blood.v81.2.337.337.

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Abstract We studied the effect of interleukin-4 (IL–4) on the lipopolysaccharide (LPS) induction of two immediate early genes c-fos and c-jun. These genes encode proteins that form the dimeric complex activator protein-1 (AP-1), which is active as a transcriptional factor. Maximal accumulation of either c-fos and c-jun messenger RNA (mRNA) occurred 30 minutes after LPS addition. When cells were treated with IL–4 for 5 hours before LPS activation, both the c-fos and the c-jun mRNA expression was decreased. The inhibition of c-fos and c-jun expression by IL-4 in LPS-treated cells was shown to be due to a lower transcription rate of the c-fos and c-jun genes. IL–4 did not affect the stability of the c-fos and c-jun transcripts. Finally, using electrophoretic mobility shift assays, evidence was obtained that IL-4 inhibits LPS-induced expression of AP-1 protein. These data indicate that IL-4 suppresses the induction of transcription factors in human activated monocytes.

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Dokter, WH, MT Esselink, MR Halie et E. Vellenga. « Interleukin-4 inhibits the lipopolysaccharide-induced expression of c- jun and c-fos messenger RNA and activator protein-1 binding activity in human monocytes ». Blood 81, n^o 2 (15 janvier 1993) : 337–43. http://dx.doi.org/10.1182/blood.v81.2.337.bloodjournal812337.

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We studied the effect of interleukin-4 (IL–4) on the lipopolysaccharide (LPS) induction of two immediate early genes c-fos and c-jun. These genes encode proteins that form the dimeric complex activator protein-1 (AP-1), which is active as a transcriptional factor. Maximal accumulation of either c-fos and c-jun messenger RNA (mRNA) occurred 30 minutes after LPS addition. When cells were treated with IL–4 for 5 hours before LPS activation, both the c-fos and the c-jun mRNA expression was decreased. The inhibition of c-fos and c-jun expression by IL-4 in LPS-treated cells was shown to be due to a lower transcription rate of the c-fos and c-jun genes. IL–4 did not affect the stability of the c-fos and c-jun transcripts. Finally, using electrophoretic mobility shift assays, evidence was obtained that IL-4 inhibits LPS-induced expression of AP-1 protein. These data indicate that IL-4 suppresses the induction of transcription factors in human activated monocytes.

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Akieda-Asai, Sayaka, Hao Ma et Yukari Date. « Palmitic acid induces guanylin gene expression through the Toll-like receptor 4/nuclear factor-κB pathway in rat macrophages ». American Journal of Physiology-Cell Physiology 317, n^o 6 (1 décembre 2019) : C1239—C1246. http://dx.doi.org/10.1152/ajpcell.00081.2019.

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Recently, we showed that double-transgenic rats overexpressing guanylin (Gn), a bioactive peptide, and its receptor, guanylyl cyclase-C (GC-C), specifically in macrophages demonstrate an antiobesity phenotype and low-expression levels of proinflammatory cytokines in the mesenteric fat even when fed a high-fat diet. Here, we examined the levels and mechanism of Gn and GC-C transcription following saturated fatty acid and lipopolysaccharide (LPS), an activator of Toll-like receptor 4 (TLR4), exposure by using the NR8383 macrophage cell line. In addition, the levels of guanylin and cGMP were increased by addition of either palmitic acid or LPS. Next, we investigated the interaction of the gene transcription and nuclear factor-κB (NF-κB) by using an NF-κB inhibitor and chromatin immunoprecipitation assay. We showed that palmitic acid induced Gn gene expression via TLR4 and NF-κB. Moreover, we demonstrated that NF-κB binding to the Gn promoter was responsible for the induction of gene transcription by palmitic acid or LPS. Our results indicate that saturated fatty acids such as palmitic acid activate Gn gene expression via the NF-κB pathway, raising the possibility that the activated Gn-GC-C system may contribute to the inhibition of high-fat diet-induced proinflammatory cytokines in macrophages.

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Blais, Jaime D., Vasilisa Filipenko, Meixia Bi, Heather P. Harding, David Ron, Costas Koumenis, Bradly G. Wouters et John C. Bell. « Activating Transcription Factor 4 Is Translationally Regulated by Hypoxic Stress ». Molecular and Cellular Biology 24, n^o 17 (1 septembre 2004) : 7469–82. http://dx.doi.org/10.1128/mcb.24.17.7469-7482.2004.

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ABSTRACT Hypoxic stress results in a rapid and sustained inhibition of protein synthesis that is at least partially mediated by eukaryotic initiation factor 2α (eIF2α) phosphorylation by the endoplasmic reticulum (ER) kinase PERK. Here we show through microarray analysis of polysome-bound RNA in aerobic and hypoxic HeLa cells that a subset of transcripts are preferentially translated during hypoxia, including activating transcription factor 4 (ATF4), an important mediator of the unfolded protein response. Changes in mRNA translation during the unfolded protein response are mediated by PERK phosphorylation of the translation initiation factor eIF2α at Ser-51. Similarly, PERK is activated and is responsible for translational regulation under hypoxic conditions, while inducing the translation of ATF4. The overexpression of a C-terminal fragment of GADD34 that constitutively dephosphorylates eIF2α was able to attenuate the phosphorylation of eIF2α and severely inhibit the induction of ATF4 in response to hypoxic stress. These studies demonstrate the essential role of ATF4 in the response to hypoxic stress, define the pathway for its induction, and reveal that GADD34, a target of ATF4 activation, negatively regulates the eIF2α-mediated inhibition of translation. Taken with the concomitant induction of additional ER-resident proteins identified by our microarray analysis, this study suggests an important integrated response between ER signaling and the cellular adaptation to hypoxic stress.

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Xu, Lingbo, Huiping Zhang, Yanhua Wang, Anning Yang, Xiaoyan Dong, Lingyu Gu, Dayue Liu, Ning Ding et Yideng Jiang. « FABP4 activates the JAK2/STAT2 pathway via Rap1a in the homocysteine-induced macrophage inflammatory response in ApoE−/− mice atherosclerosis ». Laboratory Investigation 102, n^o 1 (1 novembre 2021) : 25–37. http://dx.doi.org/10.1038/s41374-021-00679-2.

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AbstractAtherosclerosis is a chronic inflammatory vascular disease, and inflammation plays a critical role in its formation and progression. Elevated serum homocysteine (Hcy) is an independent risk factor for atherosclerosis. Previous studies have shown that fatty acid binding protein 4 (FABP4) plays an important role in macrophage inflammation and lipid metabolism in atherosclerosis induced by Hcy. However, the underlying molecular mechanism of FABP4 in Hcy-induced macrophage inflammation remains unknown. In this study, we found that FABP4 activated the Janus kinase 2/signal transducer and activator of transcription 2 (JAK2/STAT2) pathway in macrophage inflammation induced by Hcy. Of note, we further observed that ras-related protein Rap-1a (Rap1a) induced the Tyr416 phosphorylation and membrane translocation of non-receptor tyrosine kinase (c-Src) to activate the JAK2/STAT2 pathway. In addition, the suppressor of cytokine signaling 1 (SOCS1)—a transcriptional target of signal transducer and activator of transcription (STATs) inhibited the JAK2/STAT2 pathway and Rap1a expression via a negative feedback loop. In summary, these results demonstrated that FABP4 promotes c-Src phosphorylation and membrane translocation via Rap1a to activate the JAK2/STAT2 pathway, contributing to Hcy-accelerated macrophage inflammation in ApoE−/− mice.

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Jiang, Tao, Qingzhen Chen, Min Shao, Zhen Shen, Gang Wang, Qinsheng Wang et Zhenming Zeng. « Upregulation of signal transducer and activator of transcription 4 promotes osteoblast activity by activating AMP-activated protein kinase based on cationic liposome transfection ». Materials Express 10, n^o 11 (1 novembre 2020) : 1836–45. http://dx.doi.org/10.1166/mex.2020.1822.

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Activation of Protein Kinase AMP-Activated Catalytic Subunit Alpha (AMPKα) is an important regulatory pathway for osteogenic differentiation. STAT4 acts as a transcriptional activity factor to regulate the transcription of many genes and is potentially a regulatory factor for AMPKα transcription activity. To confirm the regulatory effect of STAT4 on AMPKα and the effect of STAT4 on osteogenic differentiation, the promoter sequence of AMPKα was analyzed via bioinformatics, the STAT4 overexpression vector was constructed and transfected into human osteoblast-like cells MG-63 by cationic liposome, fluorescence quantitative PCR (RT-qPCR) and western blotting technologies were used to detect the effect of STAT4 on the expression of AMPKα. MTT and ALP activity assays were also used to verify the effect of STAT4 on the proliferation and maturation of osteoblasts by regulating AMPKα expression. Our results showed that STAT4 was a co-transcriptional regulator of AMPKα1 and AMPKα2, which combined the enrichment region of CpG on the promoter sequence of AMPKα1/2. Overexpression of STAT4 significantly increased the expression of AMPKα1 and AMPKα2, which promoted the proliferation and maturation of osteoblasts. We concluded that STAT4 was a transcriptional activator of AMPKα and promoting STAT4 expression enhances the proliferation and differentiation activity of AMPKα in osteoblasts.

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Ishitani, Tohru, Jun Ninomiya-Tsuji et Kunihiro Matsumoto. « Regulation of Lymphoid Enhancer Factor 1/T-Cell Factor by Mitogen-Activated Protein Kinase-Related Nemo-Like Kinase-Dependent Phosphorylation in Wnt/β-Catenin Signaling ». Molecular and Cellular Biology 23, n^o 4 (15 février 2003) : 1379–89. http://dx.doi.org/10.1128/mcb.23.4.1379-1389.2003.

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ABSTRACT The Wnt/β-catenin signaling pathway regulates many developmental processes by modulating gene expression. Wnt signaling induces the stabilization of cytosolic β-catenin, which then associates with lymphoid enhancer factor and T-cell factor (LEF-1/TCF) to form a transcription complex that activates Wnt target genes. Previously, we have shown that a specific mitogen-activated protein (MAP) kinase pathway involving the MAP kinase kinase kinase TAK1 and MAP kinase-related Nemo-like kinase (NLK) suppresses Wnt signaling. In this study, we investigated the relationships among NLK, β-catenin, and LEF-1/TCF. We found that NLK interacts directly with LEF-1/TCF and indirectly with β-catenin via LEF-1/TCF to form a complex. NLK phosphorylates LEF-1/TCF on two serine/threonine residues located in its central region. Mutation of both residues to alanine enhanced LEF-1 transcriptional activity and rendered it resistant to inhibition by NLK. Phosphorylation of TCF-4 by NLK inhibited DNA binding by the β-catenin-TCF-4 complex. However, this inhibition was abrogated when a mutant form of TCF-4 was used in which both threonines were replaced with valines. These results suggest that NLK phosphorylation on these sites contributes to the down-regulation of LEF-1/TCF transcriptional activity.

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KUROKI, Mitsuyuki, et Joseph T. O'FLAHERTY. « Extracellular signal-regulated protein kinase (ERK)-dependent and ERK-independent pathways target STAT3 on serine-727 in human neutrophils stimulated by chemotactic factors and cytokines ». Biochemical Journal 341, n^o 3 (26 juillet 1999) : 691–96. http://dx.doi.org/10.1042/bj3410691.

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STAT3 (signal transducer and activator of transcription 3) is a latent transcription factor that is activated by tyrosine phosphorylation (Tyr-705) in cells stimulated with cytokines or growth factors. Recent studies suggest that one or more cytoplasmic serine kinases also phosphorylate STAT3 and are necessary for maximal gene activation. Here we demonstrate, with a site-specific antibody, that STAT3 is phosphorylated on Ser-727 in human neutrophils stimulated with chemotactic factors (N-formyl-methionyl-leucyl-phenylalanine and complement C5a), cytokines [granulocyte/macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF)], or a protein kinase C activator (PMA). (2-Amino-3′-methoxyphenyl)oxanaphthalen-4-one (PD 98059), an inhibitor of extracellular signal-regulated protein kinase (ERK) activation, blocked the serine phosphorylation of STAT3 induced by chemotactic factors or PMA. The drug was less effective on cytokines: it virtually abolished the response to GM-CSF that occurred 5 min after stimulation but only partly decreased those at 15-30 min and did not appreciably alter responses to G-CSF regardless of incubation time. 1-(5-Isoquinolinylsulphonyl)-2-methylpiperazine dihydrochloride (H7), an inhibitor of a putative STAT3 serine kinase, and 4-(4-fluorophenyl)-2-(4-methylsulphinylphenyl)-5-(4-pyridyl) 1H-imidazole (SB 203580), an inhibitor of p38 mitogen-activated protein (MAP) kinase, did not dampen any of these serine phosphorylation responses. We propose that neutrophils use both ERK-dependent and ERK-independent pathways to phosphorylate Ser-727 on STAT3. The former pathway is recruited by all ERK-activating stimuli, whereas the latter pathway uses an undefined serine kinase and is recruited selectively by cytokines.

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Wong, Matthew Man-Kin, Sancy Mary Joyson, Heiko Hermeking et Sung Kay Chiu. « Transcription Factor AP4 Mediates Cell Fate Decisions : To Divide, Age, or Die ». Cancers 13, n^o 4 (8 février 2021) : 676. http://dx.doi.org/10.3390/cancers13040676.

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Activating Enhancer-Binding Protein 4 (AP4)/transcription factor AP4 (TFAP4) is a basic-helix-loop-helix-leucine-zipper transcription factor that was first identified as a protein bound to SV40 promoters more than 30 years ago. Almost 15 years later, AP4 was characterized as a target of the c-Myc transcription factor, which is the product of a prototypic oncogene that is activated in the majority of tumors. Interestingly, AP4 seems to represent a central hub downstream of c-Myc and N-Myc that mediates some of their functions, such as proliferation and epithelial-mesenchymal transition (EMT). Elevated AP4 expression is associated with progression of cancer and poor patient prognosis in multiple tumor types. Deletion of AP4 in mice points to roles of AP4 in the control of stemness, tumor initiation and adaptive immunity. Interestingly, ex vivo AP4 inactivation results in increased DNA damage, senescence, and apoptosis, which may be caused by defective cell cycle progression. Here, we will summarize the roles of AP4 as a transcriptional repressor and activator of target genes and the contribution of protein and non-coding RNAs encoded by these genes, in regulating the above mentioned processes. In addition, proteins interacting with or regulating AP4 and the cellular signaling pathways altered after AP4 dysregulation in tumor cells will be discussed.

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Jiang, Hong, Ye Sen Zhu, Hui Xu, Yu Sun et Qi Fang Li. « Inflammatory stimulation and hypoxia cooperatively activate HIF-1α in bronchial epithelial cells : involvement of PI3K and NF-κB ». American Journal of Physiology-Lung Cellular and Molecular Physiology 298, n^o 5 (mai 2010) : L660—L669. http://dx.doi.org/10.1152/ajplung.00394.2009.

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The transcription factor hypoxia-inducible factor (HIF)-1 plays a central physiological role in oxygen and energy homeostasis, and is activated during hypoxia by stabilization of the subunit HIF-1α. Recent studies have demonstrated that non-hypoxic stimuli can also activate HIF-1α in a cell-specific manner. Here, we demonstrate that stimulation of BEAS-2B cells and primary human bronchial epithelial cells by proinflammatory cytokines TNFα/IL-4 strongly induced expression and transcriptional activity of HIF-1α under normoxic conditions and amplified hypoxic HIF-1α activation. TNFα/IL-4 stimulated de novo HIF-1α gene transcription and translation rather than affected HIF-1α protein degradation and mRNA decay process. The activation of HIF-1α by TNFα/IL-4 was countered by the phosphoinositol 3-kinase (PI3K) inhibitor LY-294002 and rapamycin, an antagonist of mammalian target of rapamycin (mTOR), but not by inhibition of the MAPK pathway. In line, TNFα/IL-4 also activated NF-κB, whereas blocking of NF-κB by an inhibitor or silencing NF-κB subunit p65 attenuated HIF-1α activation by TNFα/IL-4. We also found the collaborative induction of VEGF, a potent angiogenic factor required for airway remodeling, by TNFα/IL-4 and hypoxia partially via HIF-1α pathway in BEAS-2B cells. This study reports the previously unsuspected collaborative regulation of HIF-1α by TNFα/IL-4 and hypoxia in bronchial epithelial cells partially via PI3K-mTOR and NF-κB pathway, and thereby will lead to the elucidation of the importance of HIF-1 in integrating inflammatory and hypoxic response in the pathogenesis of airway diseases.

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Lieberson, Rebecca, Kerri A. Mowen, Kathryn D. McBride, Veronica Leautaud, Xiankui Zhang, Woong-Kyung Suh, Lin Wu et Laurie H. Glimcher. « Tumor Necrosis Factor Receptor–Associated Factor (Traf)2 Represses the T Helper Cell Type 2 Response through Interaction with Nfat-Interacting Protein (Nip45) ». Journal of Experimental Medicine 194, n^o 1 (2 juillet 2001) : 89–98. http://dx.doi.org/10.1084/jem.194.1.89.

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Recently we have identified a novel protein NIP45 (nuclear factor of activated T cells [NFAT]-interacting protein) which substantially augments interleukin (IL)-4 gene transcription. The provision of NIP45 together with NFAT and the T helper cell type 2 (Th2)-specific transcription factor c-Maf to cells normally refractory to IL-4 production, such as B cells or Th1 clones, results in substantial IL-4 secretion to levels that approximate those produced by primary Th2 cells. In studies designed to further our understanding of NIP45 activity, we have uncovered a novel facet of IL-4 gene regulation. We present evidence that members of the tumor necrosis factor receptor–associated factor (TRAF) family of proteins, generally known to function as adapter proteins that transduce signals from the tumor necrosis factor receptor superfamily, contribute to the repression of IL-4 gene transcription and that this effect is mediated through their interaction with NIP45.

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Schultz, C. L., P. Rothman, R. Kühn, M. Kehry, W. Müller, K. Rajewsky, F. Alt et R. L. Coffman. « T helper cell membranes promote IL-4-independent expression of germ-line C gamma 1 transcripts in B cells. » Journal of Immunology 149, n^o 1 (1 juillet 1992) : 60–64. http://dx.doi.org/10.4049/jimmunol.149.1.60.

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Abstract Studies using plasma membranes from activated Th cell clones (Th membranes) to stimulate B cells have shown that both a contact-mediated activation signal plus Th-derived cytokines are required for antibody production. In order to clearly separate and define the role of these two signals in isotype switching, B cells were stimulated with Th membranes in the presence or absence of cytokines, and the transcriptional activity of the unrearranged H chain loci was determined. In the presence of Th membranes, two known switch factors were shown to specifically induce germ-line transcription of the same H chain loci as in LPS-stimulated B cells (IL-4 induced C gamma 1 and C epsilon transcription, transforming growth factor-beta induced C alpha transcription). The contact-mediated activation signal provided by the Th membranes, in the absence of any added cytokines, resulted in the specific induction of C gamma 1 germ-line transcription, and thus functioned as a switch signal for IgG1. These findings provide a mechanism for previously observed IL-4-independent isotype switching to IgG1.

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Weiss, D. L., J. Hural, D. Tara, L. A. Timmerman, G. Henkel et M. A. Brown. « Nuclear factor of activated T cells is associated with a mast cell interleukin 4 transcription complex. » Molecular and Cellular Biology 16, n^o 1 (janvier 1996) : 228–35. http://dx.doi.org/10.1128/mcb.16.1.228.

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Interleukin 4 (IL-4), an immunoregulatory cytokine, is produced only by a subset of activated T cells and cells of the mast cell-basophil lineage. The production of IL-4 by mast cells likely represents a significant source of this protein in local immune-inflammatory responses in the skin, brain, gastrointestinal, and respiratory tracts, in which mast cells are prevalent. In the present study, the cis- and trans-acting elements that control inducible mast cell IL-4 gene transcription were examined and compared with those that function in T cells. We demonstrate that, as in T cells, sequences between bp -87 and -70 are critical for protein association and activation-dependent gene transcription and that this region (termed the activation-responsive element region) is the target of an inducible, cyclosporin A-sensitive, DNA-protein interaction. When assessed by electrophoretic mobility shift assays and UV cross-linking analyses, multiple proteins in both T- and mast cell nuclear extracts associate with the activation-responsive element in vitro, and some of these appear identical. However, distinct proteins are associated with each of the complexes as well. AP-1 family members are unique to the T-cell-stimulation-dependent complex, whereas mast cell complexes contain factors that are reactive with anti-nuclear factor of activated T cells p (NF-ATp) and anti-NF-ATc antibodies but have distinct molecular masses compared with those of T-cell-derived NF-AT. Furthermore, an anti-NF-ATp-reactive factor with a molecular mass of approximately 41 kDa is present in the nuclei of unstimulated cells and binds independently of cell activation, unlike the previously described NF-AT family members. These data support the idea that there are uniquely regulated, cell lineage-specific transcription factors related to T-cell-derived NF-AT that mediate inducible IL-4 transcription in mast cells. These differences likely reflect the distinct cell surface signaling requirements for IL-4 production in T and mast cells.

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Patel, Kunal, Shu Ye et Conrad P. Hodgkinson. « Functional Toll-like receptor 4 mutations modulate the response to fibrinogen ». Thrombosis and Haemostasis 100, n^o 08 (2008) : 301–7. http://dx.doi.org/10.1160/th08-03-0179.

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SummaryFibrinogen has been implicated in atherosclerosis; in part by activating the lipopolysaccharide (LPS) receptor Toll-like receptor 4 (TLR4). The fibrinogen-TLR4 signalling pathway remains un-characterised. In human macrophages fibrinogen stimulated interleukin (IL)6 expression and ERK (extracellular signal-related kinase) phosphorylation. In HEK293-CD14-MD2 cells expressing TLR4, fibrinogen induced robust phosphorylation of ERK1, p38α and JNK and activated transcription factors NFκB, Elk-1 and AP-1 (activator protein-1).The net effect of this signaling pathway was a pro-inflammatory response characterised by IL6 and TNFα synthesis and increased IL8,matrix metalloproteinase (MMP)1, MMP9, and MCP-1 promoter activity. Two common TLR4 mutations, D299G and T399I, render the receptor LPS hyporesponsive. The effect of fibrinogen on polymorphic variant TLR4s was markedly different; enhancing activation of kinases, transcription factors, cytokine synthesis and promoter activity. This study indicates that fibrinogen activates TLR4, explaining how fibrinogen promotes inflammatory protein expression.

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Nakatake, Yuhki, Nobutaka Fukui, Yuko Iwamatsu, Shinji Masui, Kadue Takahashi, Rika Yagi, Kiyohito Yagi et al. « Klf4 Cooperates with Oct3/4 and Sox2 To Activate the Lefty1 Core Promoter in Embryonic Stem Cells ». Molecular and Cellular Biology 26, n^o 20 (5 septembre 2006) : 7772–82. http://dx.doi.org/10.1128/mcb.00468-06.

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ABSTRACT Although the POU transcription factor Oct3/4 is pivotal in maintaining self renewal of embryonic stem (ES) cells, little is known of its molecular mechanisms. We previously reported that the N-terminal transactivation domain of Oct3/4 is required for activation of Lefty1 expression (H. Niwa, S. Masui, I. Chambers, A. G. Smith, and J. Miyazaki, Mol. Cell. Biol. 22:1526-1536, 2002). Here we test whether Lefty1 is a direct target of Oct3/4. We identified an ES cell-specific enhancer upstream of the Lefty1 promoter that contains binding sites for Oct3/4 and Sox2. Unlike other known Oct3/4-Sox2-dependent enhancers, however, this enhancer element could not be activated by Oct3/4 and Sox2 in differentiated cells. By functional screening of ES-specific transcription factors, we found that Krüppel-like factor 4 (Klf4) cooperates with Oct3/4 and Sox2 to activate Lefty1 expression, and that Klf4 acts as a mediating factor that specifically binds to the proximal element of the Lefty1 promoter. DNA microarray analysis revealed that a subset of putative Oct3/4 target genes may be regulated in the same manner. Our findings shed light on a novel function of Oct3/4 in ES cells.

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Ktistaki, E., et I. Talianidis. « Chicken ovalbumin upstream promoter transcription factors act as auxiliary cofactors for hepatocyte nuclear factor 4 and enhance hepatic gene expression. » Molecular and Cellular Biology 17, n^o 5 (mai 1997) : 2790–97. http://dx.doi.org/10.1128/mcb.17.5.2790.

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Chicken ovalbumin upstream promoter transcription factors (COUP-TFs) strongly inhibit transcriptional activation mediated by nuclear hormone receptors, including hepatocyte nuclear factor 4 (HNF-4). COUP-TFs repress HNF-4-dependent gene expression by competition with HNF-4 for common binding sites found in several regulatory regions. Here we show that promoters, such as the HNF-1 promoter, which are recognized by HNF-4 but not by COUP-TFs are activated by COUP-TFI and COUP-TFII in conjunction with HNF-4 more than 100-fold above basal levels, as opposed to about 8-fold activation by HNF-4 alone. This enhancement was strictly dependent on an intact HNF-4 E domain. In vitro and in vivo evidence suggests that COUP-TFs enhance HNF-4 activity by a mechanism that involves their physical interaction with the amino acid 227 to 271 region of HNF-4. Our results indicate that in certain promoters, COUP-TFs act as auxiliary cofactors for HNF-4, orienting the HNF-4 activation domain in a more efficient configuration to achieve enhanced transcriptional activity. These findings provide new insights into the regulatory functions of COUP-TFs, suggesting their involvement in the initial activation and subsequent high-level expression of hepatic regulators, as well as in the positive and negative modulation of downstream target genes.

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Viollet, B., A. Kahn et M. Raymondjean. « Protein kinase A-dependent phosphorylation modulates DNA-binding activity of hepatocyte nuclear factor 4. » Molecular and Cellular Biology 17, n^o 8 (août 1997) : 4208–19. http://dx.doi.org/10.1128/mcb.17.8.4208.

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Hepatocyte nuclear factor 4 (HNF4), a liver-enriched transcription factor of the nuclear receptor superfamily, is critical for development and liver-specific gene expression. Here, we demonstrate that its DNA-binding activity is modulated posttranslationally by phosphorylation in vivo, ex vivo, and in vitro. In vivo, HNF4 DNA-binding activity is reduced by fasting and by inducers of intracellular cyclic AMP (cAMP) accumulation. A consensus protein kinase A (PKA) phosphorylation site located within the A box of its DNA-binding domain has been identified, and its role in phosphorylation-dependent inhibition of HNF4 DNA-binding activity has been investigated. Mutants of HNF4 in which two potentially phosphorylatable serines have been replaced by either neutral or charged amino acids were able to bind DNA in vitro with affinity similar to that of the wild-type protein. However, phosphorylation by PKA strongly repressed the binding affinity of the wild-type factor but not that of HNF4 mutants. Accordingly, in transfection assays, expression vectors for the mutated HNF4 proteins activated transcription more efficiently than that for the wild-type protein-when cotransfected with the PKA catalytic subunit expression vector. Therefore, HNF4 is a direct target of PKA which might be involved in the transcriptional inhibition of liver genes by cAMP inducers.

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WAHAB, NADIA ABDEL, SUSAN PARKER, JEAN-DANIEL SRAER et ROGER M. MASON. « The Decorin High Glucose Response Element and Mechanism of Its Activation in Human Mesangial Cells ». Journal of the American Society of Nephrology 11, n^o 9 (septembre 2000) : 1607–19. http://dx.doi.org/10.1681/asn.v1191607.

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Abstract. The decorin gene encodes a proteoglycan with putative structural and regulatory functions whose expression is markedly increased in human mesangial cells (HMC) exposed to high concentrations of glucose (15 to 30 mM). The gene has two promoters (P1 and P2) upstream of two alternative first exons. Transcripts driven by both promoters are present in HMC maintained in 4 mM D-glucose medium. After exposure to 30 mM D-glucose for 7 to 21 d, transcripts driven by P1 are markedly increased, whereas those driven by P2 decrease. Culture in 4 mM D-glucose medium containing transforming growth factor-β1 (TGF-β1) (1.25 ng/ml) has the same effect. However, addition of an excess of TGF-β neutralizing antibody to the 30 mM D-glucose cultures only partly suppressed increased decorin transcription from P1. In transformed HMC transfected with a reporter (p-SAEP) driven by P1 or P2, P1 activity increased twofold on treatment with either 30 mM D-glucose or TGF-β1 in 4 mM medium. P2 had little activity under any conditions. 5′ deletion of P1 showed that basal transcriptional activity lies within the proximal 378 bp, while the major high glucose and TGF-β response element is located in the -683 to -583-bp region. A putative cAMP response-like sequence (TGACGTTT) lies within this region. Electrophoretic mobility shift assays revealed the same pattern of multiple complexes between oligonucleotides containing this sequence and nuclear proteins extracted from HMC maintained in either 4 or 30 mM D-glucose conditions, but the latter were more prominent. cAMP response element binding protein (CREB) was identified as one transcription factor forming these complexes but other factors remain unidentified. Increased levels of phospho-(Ser 133) CREB were found in HMC exposed to 30 mM D-glucose. High glucose also activated and led to nuclear translocation of p42/44 mitogen-activated protein kinase and p38 mitogen-activated protein kinase, both of which can activate CREB by phosphorylation of serine 133.

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Zhu, Meng, Jake Cornwall-Scoones, Peizhe Wang, Charlotte E. Handford, Jie Na, Matt Thomson et Magdalena Zernicka-Goetz. « Developmental clock and mechanism of de novo polarization of the mouse embryo ». Science 370, n^o 6522 (10 décembre 2020) : eabd2703. http://dx.doi.org/10.1126/science.abd2703.

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Embryo polarization is critical for mouse development; however, neither the regulatory clock nor the molecular trigger that it activates is known. Here, we show that the embryo polarization clock reflects the onset of zygotic genome activation, and we identify three factors required to trigger polarization. Advancing the timing of transcription factor AP-2 gamma (Tfap2c) and TEA domain transcription factor 4 (Tead4) expression in the presence of activated Ras homolog family member A (RhoA) induces precocious polarization as well as subsequent cell fate specification and morphogenesis. Tfap2c and Tead4 induce expression of actin regulators that control the recruitment of apical proteins on the membrane, whereas RhoA regulates their lateral mobility, allowing the emergence of the apical domain. Thus, Tfap2c, Tead4, and RhoA are regulators for the onset of polarization and cell fate segregation in the mouse.

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Berton, M. T., et L. A. Linehan. « IL-4 activates a latent DNA-binding factor that binds a shared IFN-gamma and IL-4 response element present in the germ-line gamma 1 Ig promoter. » Journal of Immunology 154, n^o 9 (1 mai 1995) : 4513–25. http://dx.doi.org/10.4049/jimmunol.154.9.4513.

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Abstract IL-4 regulates transcription of the germ-line gamma 1 Ig gene in murine B cells and by doing so targets this isotype for switch recombination by an unknown mechanism. In this study, we have identified an IL-4-induced DNA-binding protein factor in murine B cells designated NF-IL-4-gamma 1. This factor binds specifically to a site within a 13-bp DNA sequence extending from -125 to -113 (5' CATTCACATGAAG 3') in the germ-line gamma 1 promoter and shown previously to be important for IL-4-responsive transcription. This sequence is highly homologous to the IFN-gamma activation site or GAS, and competitive binding studies demonstrate that NF-IL-4-gamma 1 can also bind to GAS elements in the promoters of two IFN-gamma-responsive genes and to an IL-4-responsive element in the germ-line epsilon Ig promoter. NF-IL-4-gamma 1 is rapidly induced in the absence of de novo protein synthesis and expression is sustained through day 4 of in vitro culture with IL-4 and LPS. Induction of NF-IL-4-gamma 1 is inhibited by the kinase inhibitor staurosporine and the factor itself requires phosphorylation for binding activity. The binding specificity and expression characteristics of NF-IL-4-gamma 1 suggest identity with other recently described IL-4-activated, GAS-binding factors that are members of the signal transducers and activators of transcription (STAT) family of cytokine-responsive transcription factors.

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Luhr, Morten, Maria Lyngaas Torgersen, Paula Szalai, Adnan Hashim, Andreas Brech, Judith Staerk et Nikolai Engedal. « The kinase PERK and the transcription factor ATF4 play distinct and essential roles in autophagy resulting from tunicamycin-induced ER stress ». Journal of Biological Chemistry 294, n^o 20 (29 mars 2019) : 8197–217. http://dx.doi.org/10.1074/jbc.ra118.002829.

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Endoplasmic reticulum (ER) stress is thought to activate autophagy via unfolded protein response (UPR)-mediated transcriptional up-regulation of autophagy machinery components and modulation of microtubule-associated protein 1 light chain 3 (LC3). The upstream UPR constituents pancreatic EIF2-α kinase (PERK) and inositol-requiring enzyme 1 (IRE1) have been reported to mediate these effects, suggesting that UPR may stimulate autophagy via PERK and IRE1. However, how the UPR and its components affect autophagic activity has not been thoroughly examined. By analyzing the flux of LC3 through the autophagic pathway, as well as the sequestration and degradation of autophagic cargo, we here conclusively show that the classical ER stressor tunicamycin (TM) enhances autophagic activity in mammalian cells. PERK and its downstream factor, activating transcription factor 4 (ATF4), were crucial for this induction, but surprisingly, IRE1 constitutively suppressed autophagic activity. TM-induced autophagy required autophagy-related 13 (ATG13), Unc-51–like autophagy-activating kinases 1/2 (ULK1/ULK2), and GABA type A receptor–associated proteins (GABARAPs), but interestingly, LC3 proteins appeared to be redundant. Strikingly, ATF4 was activated independently of PERK in both LNCaP and HeLa cells, and our further examination revealed that ATF4 and PERK regulated autophagy through separate mechanisms. Specifically, whereas ATF4 controlled transcription and was essential for autophagosome formation, PERK acted in a transcription-independent manner and was required at a post-sequestration step in the autophagic pathway. In conclusion, our results indicate that TM-induced UPR activates functional autophagy, and whereas IRE1 is a negative regulator, PERK and ATF4 are required at distinct steps in the autophagic pathway.

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Saigusa, Ryosuke, Yoshihide Asano, Takashi Taniguchi, Takashi Yamashita, Yohei Ichimura, Takehiro Takahashi, Tetsuo Toyama et al. « Multifaceted contribution of the TLR4-activated IRF5 transcription factor in systemic sclerosis ». Proceedings of the National Academy of Sciences 112, n^o 49 (23 novembre 2015) : 15136–41. http://dx.doi.org/10.1073/pnas.1520997112.

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Systemic sclerosis (SSc) is a multisystem autoimmune disorder with clinical manifestations resulting from tissue fibrosis and extensive vasculopathy. A potential disease susceptibility gene for SSc is IFN regulatory factor 5 (IRF5), whose SNP is associated with milder clinical manifestations; however, the underlying mechanisms of this association remain elusive. In this study we examined IRF5-deficient (Irf5−/−) mice in the bleomycin-treated SSc murine model. We show that dermal and pulmonary fibrosis induced by bleomycin is attenuated in Irf5−/− mice. Interestingly, we find that multiple SSc-associated events, such as fibroblast activation, inflammatory cell infiltration, endothelial-to-mesenchymal transition, vascular destabilization, Th2/Th17 skewed immune polarization, and B-cell activation, are suppressed in these mice. We further provide evidence that IRF5, activated by Toll-like receptor 4 (TLR4), binds to the promoters of various key genes involved in SSc disease pathology. These observations are congruent with the high level of expression of IRF5, TLR4, and potential endogenous TLR4 ligands in SSc skin lesions. Our study sheds light on the TLR4-IRF5 pathway in the pathology of SSc with clinical implications of targeting the IRF5 pathways in the suppression of disease development.

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Hatzis, Pantelis, Irene Kyrmizi et Iannis Talianidis. « Mitogen-Activated Protein Kinase-Mediated Disruption of Enhancer-Promoter Communication Inhibits Hepatocyte Nuclear Factor 4α Expression ». Molecular and Cellular Biology 26, n^o 19 (1 octobre 2006) : 7017–29. http://dx.doi.org/10.1128/mcb.00297-06.

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ABSTRACT Hepatocyte nuclear factor 4 (HNF-4) is a key member of the transcription factor network regulating hepatocyte differentiation and function. Activation of the HNF-4 gene involves physical interaction between a distant enhancer and the proximal promoter region, bound by distinct sets of transcription factors. Here we report that, upon mitogen-activated protein (MAP) kinase activation, HNF-4 expression is downregulated in human hepatoma cells. This effect is mediated by the loss of CEBPα expression. During MAP kinase signaling, the recruitment of HNF-3β and HNF-1α to the HNF-4 enhancer and RNA polymerase II to the proximal HNF-4 promoter was compromised. CBP, Brg1, and TFIIB were also dissociated from the HNF-4 regulatory regions, and the enhancer-promoter complex was disrupted. Interestingly, the extent of nucleosome acetylation did not decrease at either regulatory region, and HNF-6 and HNF-1α, as well as components of the TFIID, remained associated with the proximal promoter during the repressed state. The results point to an absolute requirement of enhancer-promoter communication for maintaining the active state of the HNF-4 gene and provide evidence for a molecular bookmarking mechanism, which may contribute to the prevention of permanent silencing of the locus during the repressed state.

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Barnes, Peter J. « Anti-inflammatory Actions of Glucocorticoids : Molecular Mechanisms ». Clinical Science 94, n^o 6 (1 juin 1998) : 557–72. http://dx.doi.org/10.1042/cs0940557.

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1. Glucocorticoids are widely used for the suppression of inflammation in chronic inflammatory diseases such as asthma, rheumatoid arthritis, inflammatory bowel disease and autoimmune diseases, all of which are associated with increased expression of inflammatory genes. The molecular mechanisms involved in this antiinflammatory action of glucocorticoids is discussed, particularly in asthma, which accounts for the highest clinical use of these agents. 2. Glucocorticoids bind to glucocorticoid receptors in the cytoplasm which then dimerize and translocate to the nucleus, where they bind to glucocorticoid response elements (GRE) on glucocorticoid-responsive genes, resulting in increased transcription. Glucocorticoids may increase the transcription of genes coding for antiinflammatory proteins, including lipocortin-1, interleukin-10, interleukin-1 receptor antagonist and neutral endopeptidase, but this is unlikely to account for all of the widespread anti-inflammatory actions of glucocorticoids. 3. The most striking effect of glucocorticoids is to inhibit the expression of multiple inflammatory genes (cytokines, enzymes, receptors and adhesion molecules). This cannot be due to a direct interaction between glucocorticoid receptors and GRE, as these binding sites are absent from the promoter regions of most inflammatory genes. It is more likely to be due to a direct inhibitory interaction between activated glucocorticoid receptors and activated transcription factors, such as nuclear factor-κB and activator protein-1, which regulate the inflammatory gene expression. 4. It is increasingly recognized that glucocorticoids change the chromatin structure. Glucocorticoid receptors also interact with CREB-binding protein (CBP), which acts as a co-activator of transcription, binding several other transcription factors that compete for binding sites on this molecule. Increased transcription is associated with uncoiling of DNA wound around histone and this is secondary to acetylation of the histone residues by the enzymic action of CBP. Glucocorticoids may lead to deacetylation of histone, resulting in tighter coiling of DNA and reduced access of transcription factors to their binding sites, thereby suppressing gene expression. 5. Rarely patients with chronic inflammatory diseases fail to respond to glucocorticoids, although endocrine function of steroids is preserved. This may be due to excessive formation of activator protein-1 at the inflammatory site, which consumes activated glucocorticoid receptors so that they are not available for suppressing inflammatory genes. 6. This new understanding of glucocorticoid mechanisms may lead to the development of novel steroids with less risk of side effects (which are due to the endocrine and metabolic actions of steroids). ‘Dissociated’ steroids which are more active in transrepression (interaction with transcription factors) than transactivation (GRE binding) have now been developed. Some of the transcription factors that are inhibited by glucocorticoid, such as nuclear factor-κB, are also targets for novel anti-inflammatory therapies.

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Delphin, S., et J. Stavnezer. « Characterization of an interleukin 4 (IL-4) responsive region in the immunoglobulin heavy chain germline epsilon promoter : regulation by NF-IL-4, a C/EBP family member and NF-kappa B/p50. » Journal of Experimental Medicine 181, n^o 1 (1 janvier 1995) : 181–92. http://dx.doi.org/10.1084/jem.181.1.181.

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A large body of data indicate that antibody class switching is directed by cytokines by inducing or repressing transcription from unrearranged, or germline, CH genes. Interleukin 4 (IL-4) induces transcription of the germline C epsilon genes in activated B cells and subsequently, cells in this population will undergo switch recombination to immunoglobulin E. Furthermore, the data suggest that transcription of germline C epsilon genes is required for class switching. In this paper we define DNA elements required for induction of transcription of the germline C epsilon genes by IL-4. To do this, segments of DNA from the 5' flank of the initiation sites for germline epsilon RNA were ligated to a luciferase reporter gene and transfected into two mouse B cell lines, one of which can be induced to switch to IgE. By analysis of a series of 5' deletion constructs and linker-scanning mutations, we demonstrate that a 46-bp segment (residing at -126/-79 relative to the first RNA initiation site) contains an IL-4 responsive region. By electrophoretic mobility shift assays, we find that this segment binds three transcription factors: the recently described NF-IL4, one or more members of the C/EBP family of transcription factors, and NF-kappa B/p50. Mutation of any of the binding sites for these three factors abolishes or reduces IL-4 inducibility of the epsilon promoter. A 27-bp segment within this IL-4 response region containing binding sites for NF-IL4 and a C/EBP factor is sufficient to transfer IL-4 inducibility to a minimal c-fos promoter.

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Thomas, M. J., A. M. Gronowski, S. A. Berry, P. L. Bergad et P. Rotwein. « Growth hormone rapidly activates rat serine protease inhibitor 2.1 gene transcription and induces a DNA-binding activity distinct from those of Stat1, -3, and -4. » Molecular and Cellular Biology 15, n^o 1 (janvier 1995) : 12–18. http://dx.doi.org/10.1128/mcb.15.1.12.

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Transcriptional regulation by growth hormone (GH) represents the culmination of signal transduction pathways that are initiated by the cell surface GH receptor and are targeted to the nucleus. Recent studies have demonstrated that the activated GH receptor can stimulate Stat1, a cytoplasmic transcription factor that becomes tyrosine phosphorylated and translocates to the nucleus, where it can interact with specific DNA sequences to modulate gene expression. GH also has been found to induce protein binding to a portion of the rat serine protease inhibitor (Spi) 2.1 gene promoter that is required for GH-induced transcription of Spi 2.1. Using GH-deficient hypophysectomized rats as a model, we show that GH treatment rapidly and potently induces both nuclear Spi 2.1 mRNA expression in the liver and specific nuclear protein binding to a 45-bp segment of the Spi 2.1 gene promoter. A GH-inducible gel-shifted complex appears within 15 min of systemic hormone administration and can be inhibited by an antiphosphotyrosine monoclonal antibody but is not blocked by a polyclonal antiserum to Stat1, Stat3, or Stat4, even though the nucleotide sequence contains two gamma interferon-activated sequence-like elements that could interact with STAT proteins. By Southwestern (DNA-protein) blot analysis, approximately 41- and 35-kDa GH-inducible proteins were detected in hepatic nuclear extracts with the Spi 2.1 DNA probe. Thus, a GH-activated signaling pathway stimulates Spi 2.1 gene expression through a unique mechanism that does not appear to involve known members of the STAT family of transcription factors.

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Niesner, Uwe, Inka Albrecht, Marko Janke, Cornelia Doebis, Christoph Loddenkemper, Maria H. Lexberg, Katharina Eulenburg et al. « Autoregulation of Th1-mediated inflammation by twist1 ». Journal of Experimental Medicine 205, n^o 8 (28 juillet 2008) : 1889–901. http://dx.doi.org/10.1084/jem.20072468.

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The basic helix-loop-helix transcriptional repressor twist1, as an antagonist of nuclear factor κB (NF-κB)–dependent cytokine expression, is involved in the regulation of inflammation-induced immunopathology. We show that twist1 is expressed by activated T helper (Th) 1 effector memory (EM) cells. Induction of twist1 in Th cells depended on NF-κB, nuclear factor of activated T cells (NFAT), and interleukin (IL)-12 signaling via signal transducer and activator of transcription (STAT) 4. Expression of twist1 was transient after T cell receptor engagement, and increased upon repeated stimulation of Th1 cells. Imprinting for enhanced twist1 expression was characteristic of repeatedly restimulated EM Th cells, and thus of the pathogenic memory Th cells characteristic of chronic inflammation. Th lymphocytes from the inflamed joint or gut tissue of patients with rheumatic diseases, Crohn's disease or ulcerative colitis expressed high levels of twist1. Expression of twist1 in Th1 lymphocytes limited the expression of the cytokines interferon-γ, IL-2, and tumor necrosis factor-α, and ameliorated Th1-mediated immunopathology in delayed-type hypersensitivity and antigen-induced arthritis.

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Urekar, Craig, Kshitish K. Acharya, Preeti Chhabra et Prabhakara P. Reddi. « A 50-bp enhancer of the mouse acrosomal vesicle protein 1 gene activates round spermatid-specific transcription in vivo† ». Biology of Reproduction 101, n^o 4 (10 juillet 2019) : 842–53. http://dx.doi.org/10.1093/biolre/ioz115.

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Abstract Enhancers are cis-elements that activate transcription and play critical roles in tissue- and cell type-specific gene expression. During spermatogenesis, genes coding for specialized sperm structures are expressed in a developmental stage- and cell type-specific manner, but the enhancers responsible for their expression have not been identified. Using the mouse acrosomal vesicle protein (Acrv1) gene that codes for the acrosomal protein SP-10 as a model, our previous studies have shown that Acrv1 proximal promoter activates transcription in spermatids; and the goal of the present study was to separate the enhancer responsible. Transgenic mice showed that three copies of the −186/−135 fragment (50 bp enhancer) placed upstream of the Acrv1 core promoter (−91/+28) activated reporter expression in testis but not somatic tissues (n = 4). Immunohistochemistry showed that enhancer activity was restricted to the round spermatids. The Acrv1 enhancer failed to activate transcription in the context of a heterologous core promoter (n = 4), indicating a likely requirement for enhancer-core promoter compatibility. Chromatin accessibility assays showed that the Acrv1 enhancer assumes a nucleosome-free state in male germ cells (but not liver), indicating occupancy by transcription factors. Southwestern assays (SWA) identified specific binding of the enhancer to a testis nuclear protein of 47 kDa (TNP47). TNP47 was predominantly nuclear and becomes abundant during the haploid phase of spermatogenesis. Two-dimensional SWA revealed the isoelectric point of TNP47 to be 5.2. Taken together, this study delineated a 50-bp enhancer of the Acrv1 gene for round spermatid-specific transcription and identified a putative cognate factor. The 50-bp enhancer could become useful for delivery of proteins into spermatids.

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KISTANOVA, Elena, Helen DELL, Panayota TSANTILI, Eileen FALVEY, Christos CLADARAS et Margarita HADZOPOULOU-CLADARAS. « The activation function-1 of hepatocyte nuclear factor-4 is an acidic activator that mediates interactions through bulky hydrophobic residues ». Biochemical Journal 356, n^o 2 (24 mai 2001) : 635–42. http://dx.doi.org/10.1042/bj3560635.

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The hepatocyte nuclear factor-4 (HNF-4) contains two transcription activation domains. One domain, activation function-1 (AF-1), consists of the extreme N-terminal 24 amino acids and functions as a constitutive autonomous activator of transcription. This short transactivator belongs to the class of acidic activators, and it is predicted to adopt an amphipathic α-helical structure. Transcriptional analysis of sequential point mutations of the negatively charged residues (Asp and Glu) revealed a stepwise decrease in activity, while mutation of all acidic residues resulted in complete loss of transcriptional activity. Mutations of aromatic and hydrophobic amino acids surrounding the negatively charged residues had a much more profound effect than mutations of acidic amino acids, since even a single mutation of these residues resulted in a dramatic decrease in transactivation, thus demonstrating the importance of hydrophobic residues in AF-1 activity. Like other acidic activators, the AF-1 of HNF-4 binds the transcription factor IIB and the TATA-binding protein directly in vitro. In addition, the cAMP-response-element-binding-protein, a transcriptional adapter involved in the transactivation of a plethora of transcription factors, interacts with the AF-1 of HNF-4 and co-operates in the process of transactivation by HNF-4. The different protein targets of AF-1 suggest that the AF-1 of HNF-4 may be involved in recruiting both general transcription factors and chromatin remodelling proteins during activation of gene expression.

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