Dissertations / Theses: 'Methyltransferases'

1

Vidgren, Jukka. "Crystallographic studies on drug receptors catechol O-methyltransferase and carbonic anhydrase /." Lund : Dept. of Molecular Biophysics, Lund University, 1994. http://catalog.hathitrust.org/api/volumes/oclc/39725795.html.

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2

Vogt, Thomas. "Plant natural product glycosyl- and methyltransferases." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=984745009.

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3

Cheung, Siu-ping, and 張小屏. "Genotypic and phenotypic analysis of the thiopurine S-methyltransferase (TPMT) gene with clinical correlation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/193543.

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Immunosuppressants (such as azathioprine and 6‐mercaptopurine) are widely used in the management of patients having rheumatic diseases, inflammatory bowel diseases, hematological malignancies and organ transplant rejections. However, the adverse effects and effectiveness of these drugs are dependent on the metabolism by the enzyme, thiopurine S‐methyltransferase (TPMT), inside the body and the activity of this enzyme is determined by its genetic polymorphism. This study mainly focused on four known mutations, TPMT*2, TPMT*3A, TPMT*3B and TPMT*3C which were detected by three sets of primers, G238C, G460A and A719G targeting exons 5, 7 & 10 of the TPMT gene. Patient blood was collected from patients who had a clinical need of knowing the TPMT level (n=202). The TPMT phenotypic status of patient was determined by measuring the enzyme activity of red blood cell lysates by Enzyme‐Linked Immunosorbent Assay (ELISA) commercially available. On the other hand, the genotype was reflected by the sequencing results generated after DNA extraction from whole blood, followed by amplification, purification and DNA sequencing by the targeted primers. The majority of patients (92%) showed normal to high TPMT enzyme activity level (>17 U) and the remaining 8% was under the category of borderline activity (between 7 U to 17 U). None of them had low or deficient activity. The mean TPMT enzyme activity of all samples was 22.9 U ranging from 7.8 U to 54.1 U. No observable difference was found between male and female. The largest group of patients was having rheumatic diseases, with enzyme activity levels from 7.8 U to 54.1 U (mean of 22.8 U) which was very close to the overall findings. Also, there was no direct relationship between the lowest white blood cell count and the TPMT activity of each patient. Low white blood cell counts were not usually associated with lower TPMT enzyme activity. From the DNA sequencing results, 62.5% of the samples (n=104) had no genetic abnormalities found, 31.7% were found to have a heterozygous allele C/T and G/A at position 474 which was known to be a silent mutation with no amino acid alteration and hence was not functionally defective. Only 4.8% had heterozygous allele A/G and T/C at position 719 and one sample was found to have heterozygous allele at both positions 719 and 474. There was no significant difference in the TPMT enzymatic activity between the samples with genetic abnormalities and those without genetic abnormalities (means of TPMT enzymatic activity were 17.3 U and 21.5 U respectively, p=0.13). And also, no apparent correlation was found among the TPMT enzymatic levels, the genetic abnormalities and the disease groups. In conclusion, the individual differences in the TPMT enzyme activity were resulted from the allelic variation at the TPMT locus, it was important to fully understand the allelic variation at the TPMT gene locus. The ghenotypic analysis could be extended to the detection of all the ten exons including their spice‐site junctions and 5’ flanking promoter region of the TPMT gene by PCR single strand conformation polymorphism in future studies.
published_or_final_version
Pathology
Master
Master of Medical Sciences

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4

Zheng, Sushuang. "Structure-function analyses of Encephalitozoon cuniculi : and vaccinia virus mRNA cap (guanine N-7) methyltransferases and sinefungin resistance of Saccharomyces cerevisiae /." Access full-text from WCMC, 2008. http://proquest.umi.com/pqdweb?did=1528353811&sid=5&Fmt=2&clientId=8424&RQT=309&VName=PQD.

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5

Bonnist, Eleanor Y. M. "The investigation of DNA-methyltransferase interactions in the adenine methyltransferases using the time-resolved fluorescence of 2-aminopurine." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/3175.

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The time-resolved fluorescence of 2-aminopurine (2AP) has been used to investigate DNA base flipping by the adenine methyltransferases and to study aspects of the DNA-enzyme interaction. 2AP is an excellent fluorophore to probe base flipping in the adenine methyltransferases because, as demonstrated in the present work on M.TaqI, the 2AP is delivered into the same position inside the enzyme as the natural target adenine and with the same orientation that prepares the adenine for enzyme catalysis. 2AP emits two types of fluorescence when in DNA. The first is the well-known 370-nm emission, which emanates from 2AP as a monomer species. The second is 450-nm emission and comes from a 2AP which is π-stacked with a neighbouring DNA base, a heterodimer species. Additionally, 450-nm emission is produced by a 2AP-tyrosine or 2APphenylalanine heterodimer when a flipped 2AP is π-stacked inside a DNA-methyltransferase complex. Steady state fluorescence of the 2AP-heterodimer has been used to complement the time-resolved investigations. Combined crystal- and solution-phase studies on M.TaqI have shown that when 2AP is flipped into the active site of M.TaqI it is significantly quenched by face-to-face π- stacking with the tyrosine from the NPPY catalytic motif. Not all of the flipped bases are held inside NPPY; in a minority of complexes, the flipped 2AP experiences very little quenching within the interior of the enzyme. In the sequence of bases recognised by M.TaqI, the thymine opposite the target adenine does not actively cause base flipping, as previously suggested, however, its presence aids the successful delivery of the target base into NPPY. For the DNA-M.TaqI-cofactor ternary complex, the effect of varying the cofactor has been investigated. The use of 5’-[2(amino)ethylthio]-5’-deoxyadenosine (AETA) or sinefungin as cofactor analogue causes M.TaqI to show different base flipping behaviour compared with the natural cofactor S-adenosyl-L-methionine (SAM) and with the cofactor product S-adenosyl homocysteine (SAH). In the ternary complex containing SAM the flipped base is held the most tightly within the catalytic motif. M.TaqI mutants have been studied in which the tyrosine (Y) in the NPPY motif is mutated to alanine (A) or phenylalanine (F). Stabilisation of the flipped base inside these mutants is more reliant on edge-to-face π-stacking with phenylalanine 196 and the available hydrogen-bonding in the adenine binding pocket. The NPPF-phenylalanine does not π-stack with the flipped base as NPPY-tyrosine does. Solution-phase time-resolved fluorescence studies have confirmed that M.EcoRI and M.EcoRV use a base-flipping mechanism to extrude their target bases. For M.EcoRI, with sinefungin cofactor, the majority of the flipped 2APs are not held in the NPPF catalytic motif. When the natural SAM cofactor is used, however, the flipped 2AP strongly associates with NPPF inside M.EcoRI. Non-cognate sequence binding has been investigated, in which M.EcoRI encounters a base that is in almost the same sequence context as the methylation target. M.EcoRI forms some direct contacts with the pseudo-target adenine but does not extrude the base that is in a highly stacked position inside the duplex. The H235N mutant of M.EcoRI, measured under the same conditions as the wild-type enzyme, shows different behaviour to the wild-type enzyme in a small proportion of complexes, when bound to the cognate recognition sequence, and is far more discriminating than the wild-type when bound to the non-cognate sequence. The M.EcoRV methyltransferase was found to be less efficient at flipping its target base than with M.TaqI or M.EcoRI. When M.EcoRV binds to its GATATC recognition sequence, the base-enzyme interactions of the target (GAT) and non-target (TAT) adenine position are shown to be quite different.

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May, Kyle M. "Investigation of Protein Dynamics and Communication in Adomet-Dependent Methyltransferases: Non-Ribosomal Peptide Synthetase and Protein Arginine Methyltransferase." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7550.

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For many enzymes to function correctly they must have the freedom to display a level of dynamics or communication during their catalytic cycle. The effects that protein dynamics and communication can have are wide ranging, from changes in substrate specificity or product profiles, to speed of reaction or switching activity on or off. This project investigates the protein dynamics and communication in two separate systems, a non-ribosomal peptide synthetase (NRPS), and a protein arginine methyltransferase (PRMT). PRMT1, the enzyme responsible for 80% of arginine methylation in humans, has been implicated in a variety of disease states when functioning incorrectly. For this reason, much focus has been placed on better understanding how PRMT1 determines which products it creates and at what times. This project aims to shed light on how dynamics and communication within PRMT1 dictate its activity. We have to this point developed a protocol for creating and purifying a linked PRMT1 construct which will enable us to conduct the necessary experiments capable of answering our larger questions about the PRMT1 catalytic mechanism. Our collaborators in the Zhan lab discovered the presence of a methyltransferase (Mt) in the two NRPS systems they study, which produce two different and medically relevant compounds, bassianolide and beauvericin. The Hevel lab is well suited to study methyltransferases and so were asked to help evaluate the role of these Mt domains and how they affect the production of the relevant natural products. Achieving a more complete understanding of these systems will move us closer toward the “holy grail” of being able to manipulate and harness NRPS systems for the engineering of novel medically relevant compounds. This project has found that the Mt domain substrate specificity is affected by the surrounding protein domains, or even small portions of them.

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Fellinger, Karin. "Analysis of Protein Interactions Controlling DNA Methyltransferases." Diss., lmu, 2009. http://nbn-resolving.de/urn:nbn:de:bvb:19-98919.

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8

Jimenez, Rosales Angelica. "Methyltransferases as bioorthogonal labelling tools for proteins." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/methyltransferases-as-bioorthogonal-labelling-tools-for-proteins(27231f93-7cdd-4c2d-9f31-0adc3f38b147).html.

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Development of enzymatic labelling methods has been driven by the importance of studying molecular structures and interactions to comprehend cellular processes. Methyltransferases (MTases), which regulate genetic expression by transferring a methyl group from the cofactor S-adenosyl-L-methionine (SAM) to DNA, histones and various proteins, have been shown to accept SAM analogues with an alternative alkyl group on the sulfonium centre. These alkyl groups can be transferred to the substrate, and with a further reaction can be selectively functionalized. Thus, MTases together with SAM analogues have emerged as novel labelling tools. The project aims to use MTases to obtain an orthogonal system that can selectively use a SAM cofactor analogue to transfer functional chains to proteins with a specific motif. To achieve selectivity of the system, the SAM analogue cofactor was modified on the ribose ring; to obtain a new transferase activity of the system, the transferable methyl on the sulfonium centre was changed to a different substituent. SAM analogues were produced enzymatically with hMAT2A by using 3'-deoxy-ATP and methionine or ethionine. Mutants of SET8 and novel substrates were designed to have modifications at residues in the active site, within the vicinity of the ribose ring of SAM, and were assessed for selective activity with the new analogue cofactor. The results showed that the new cofactor 3'-deoxy-S-adenosyl-L-methionine (3'dSAM) was efficient in the mono-methylation of the substrate peptide RFRKVL, and that the mutant SET8 C270V exhibited over 13 fold MTase activity in presence of 3'dSAM and the RFRKVL substrate, in comparison with the activity with the WT sequence RHRKVL and the SAM cofactor. In addition, glutathione S-transferase (GST) was used as a model protein to express the motif RFRKVL, to transform it into a potential substrate for SET8. Assessment of the MTase activity of SET8, 3'dSAM and the novel GST substrate indicated mono-methylation of the substrate. Moreover, the motif showed no interference with GST native activity. Based on the observations, a new enzymatic system shows higher selectivity with a new analogue cofactor over SAM to effectively methylate proteins expressing the consensus RFRKVL. Work on substrates, enzymes and cofactors should continue to obtain a functional-chain transferase activity of the enzymatic system.

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9

Burgers, Wendy Anne. "DNA methyltransferases in the regulation of transcription." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621269.

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Walsh, Monica Eve. "The role of SUV methyltransferases at telomeres." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16620.

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Telomeres are nucleoprotein structures at the ends of linear chromosomes composed of 5′-TTAGGG-3′ tandem repeat arrays, bound by histone proteins and the telomere-specific binding protein complex shelterin. In somatic cells, telomeres undergo gradual attrition with each cell division, accompanied by a loss of proliferative capacity and eventual cell death. Cancer cells are required to activate a telomere maintenance mechanism in order to circumnavigate this telomere attrition, and thereby gain unlimited proliferative capacity. This can be accomplished through the activation of the ribonucleoprotein telomerase, or through the activation of a homologous recombination (HR) mediated mechanism known as Alternative Lengthening of Telomeres (ALT). Telomere specific proteins, along with telomeric nucleosomes, cap chromosome ends to prevent them from being recognised as DNA double strand breaks. Cancers that use ALT display elevated levels of telomere-specific DNA damage response (DDR) and aberrant telomeric chromatin, implicating a role for telomere chromatin in maintaining structural integrity. Tandem repeat sequences are characterised as being highly recombinogenic. In order to prevent aberrant telomere recombination events, telomeres are maintained in a heterochromatin-like state, being enriched in the H3K9me3 and H4K20me3 heterochromatin marks. The post-translational methylation of H3K9 is achieved by the histone methyl transferase SUV39 family of proteins, which function to increase chromatin compaction. Alteration of these heterochromatin marks in mice results in the induction of ALT phenotypes. As ALT telomeres rely on a HR mechanism of telomere extension, aberrations in telomeric heterochromatin are believed to mediate HR, and therefore facilitate the growth of ALT cancers. The aim of this thesis was to explore the role of SUV39 proteins, and their heterochromatic mark H3K9me3, in maintaining telomere structural integrity. By modulating the expression of SUV39 proteins in a panel of human cancer cell lines, we were able to investigate whether telomeric chromatin state affected telomere recombination, telomere protection and telomere length maintenance. Through SUV39 depletion studies, we demonstrated that loss of H3K9me3 at telomeres results in exacerbated telomere dysfunction, detected by the association of DDR proteins at telomeres. This result revealed for the first time that heterochromatin state is important to the maintenance of telomere structure. One caveat was that this increase was only observed in cells with an already high basal level of DNA damage, implying that loss of H3K9me3 was only able to perturb telomeres with underlying structural defects. This result was independent of the employed TMM of the cell. Through SUV39 overexpression studies, we demonstrated that increased compaction resulted in a decrease in DDR at telomeres only in ALT cells, suggesting that the structural defects that underlie ALT telomeres can be supressed through increased heterochromatin. Not all ALT cell lines were able to be protected from DDR, suggesting that factors other than heterochromatin mediate the extent of telomere dysfunction at these cancer cell lines. Through depletion of the telomere capping protein, telomere repeat binding protein 2 (TRF2), we revealed that SUV39 overexpression was able to confer a protective effect in certain ALT cells. This reduction in DDR, however, could not be maintained following further telomere deprotection by the depletion of both telomere repeat binding protein 1 (TRF1) and TRF2. These results suggest that while telomeric heterochromatin may have a role in telomere DDR suppression, it is not able to confer a protective role upon exhaustive telomere insult. Overall in this thesis we demonstrated that both the depletion and overexpression of SUV39 proteins did not alter telomere length in cells which utilise either ALT or telomerase-mediated telomere extension. These findings are in direct contrast to heterochromatin-based telomere length studies carried out in both mouse and swine cell lines. Furthermore, we were able to show through chromatin immunoprecipitation studies that the SUV39 family of proteins directly associate with telomeric chromatin, albeit at a very low abundance. This result provides evidence demonstrating that there is a direct interaction between telomeres and SUV39 in human cells, but its association does not regulate telomere length.

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Al-Swailem, Abdulaziz Mohammed A. "Error-prone repair induced by mutant DNA methyltransferases." Thesis, University of Sheffield, 1999. http://etheses.whiterose.ac.uk/14776/.

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Organisms utilise cytosine-5 DNA methylation to expand their repertoire of genetic transactions. Structural studies of DNA cytosine-5 methyltransferase have revealed that DNA methyltransferases incorporate nucleotide flipping into their catalytic cycle in order to access the otherwise buried pyrimidine ring from within duplex DNA. Interestingly, substituting the catalytic nucleophile Cys with Gly can produce cytotoxic forms of the bacterial methyltransferases and cause rearrangements in the DNA. In this study the generality of the cytotoxic effect has been studied on both mono and multi-specific methyltransferases. The effect of dimerisation of methyltransferases on the rearrangement event and the specificity of DNA damage have been defined. The involvement of two DNA repair proteins RecA and UmuDC has been studied. The wild type and mutant multispecific methyltransferase (M.SPRI) has been transcribed and translated in vitro and the proteins studied using surface plasmon resonance technique. The experiments described here demonstrate for the first time how a high affinity, catalytically deficient DNA methyltransferase induces error-prone deletions in E.coli.

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Blight, Sherry Kathleen. "Amber codon translation as pyrrolysine in Methanosarcina spp." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149012579.

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13

Coe, Torres Davi. "Understanding H3K36 methyltransferases in mouse embryonic stem cells." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-144706.

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Methylation of histone 3 (H3) at lysine 36 (K36) has been implicated in several biological processes, such as DNA replication, DNA repair, and transcription. To date, at least eight distinct mammalian enzymes have been described to methylate H3K36 in vitro and/or in vivo. In this work, Set2, Nsd1, and Nsd3 Venus tagged proteins were successfully expressed in mouse embryonic stem cells and, then, analyzed by confocal microscopy, mass spectrometry (MS), and chromatin immunoprecipitation sequencing (ChIP-seq). MS analysis revealed that Setd2, Nsd1, and Nsd3 do not associate in protein complexes with each other. Setd2 was associated with RNA polymerase II subunits and two transcription elongation factors (Supt5 and Supt6), whereas Nsd1 associated with the transcription factor Zfx. In contrast, Nsd3 interacted with multiple protein complexes including Kdm1b and Brd4 complexes. Interestingly, Nsd1 and Zfx seem to be bound to chromatin during cell division. ChIP-seq analysis of the H3K36 methyltransferases showed different binding profiles at transcribed genes: Nsd1 binds near the transcription start site (TSS), Setd2 loading starts near the TSS and spreads along the gene body, while, Nsd3 is preferentially enriched at the 5’ and 3’ gene regions. Sequential deletion of PWWP and zinger-finger like domains was achieved to study any possible changes in Nsd1 and Nsd3 function. Deletion of either PHD1-4 or PHD5/C5HCH domains decreased Nsd1 recruitment to chromatin. Particularly, the PHD5/C5HCH were identified as the protein-protein interface for Zfx interaction. In agreement, Zfx knockdown also decreased Nsd1 deposition at the Oct4 and Tcl1 promoter regions. Furthermore, Nsd1 depletion reduced bulk histone H3K36me2 and histone H3K36me3 loading at the coding regions of Oct4, Rif1, Brd2, and Ccnd1. In addition, Nsd1 knockdown led to an increased Zfx deposition at promoters. Our findings suggest Zfx recruits Nsd1 to its target loci, whereas Nsd1 regulates Zfx chromatin release and further contributes to transcription regulation through its H3K36 dimethylase activity. On the other hand, loss of Nsd3’s PHD5/C5HCH or PWWP domains decreased Nsd3 binding to DNA. In addition, we demonstrate that Nsd3 is recruited to target genes in a Brd4-dependent manner. Herein, we provided further insights on how H3K36 methyltransferases are regulated, and how they contribute to changes in the epigenetic landscape in mouse embryonic stem cells.fi

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Nawafa, Lotfia Shames Omar. "The contribution of methyltransferases/demethylases to renal fibrosis." Thesis, University of Newcastle upon Tyne, 2018. http://hdl.handle.net/10443/4111.

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TGF β-1 signalling regulates many cellular processes, including proliferation, differentiation, apoptosis, immune responses, and fibrogenesis. The essential role of TGF β-1/SMAD signalling in stimulating fibrogenic cells to produce extra cellular matrix proteins and promoting proliferation of myofibroblasts is widely recognised. SMAD3 is known as a mediator in TGF β- 1-induced fibrosis in the kidney. Upon activation of TGF-β receptors, SMAD2 and SMAD3 are phosphorylated and form cytoplasmic heteromeric complexes with SMAD4. These complexes translocate to the nucleus where they regulate expression of TGF β-1 target genes. Tissues undergoing fibrosis exhibit markedly increased expression of a-SMA and interstitial matrix components, such as collagen and fibronectin which are TGF β-1/SMAD3-responsive genes. The mechanism by which SMADs mediate transcriptional regulation of these genes is incompletely understood, however SMAD3-null mice are protected against renal tubulointerstitial fibrosis, glomerular sclerosis, and also fibrosis in other organs. Data from this thesis has demonstrated for the first time that methylation might be important in the regulation of SMAD3 transcriptional activity; indeed the introduction of siRNAs targeting demethylases/methyltransferases led to changes in SMAD3 transcriptional activity. The introduction of siRNAs targeting both methyltransferases and demethylases resulted in changes in α-SMA and fibronectin expression at the protein level. The work in this dissertation again confirms that TGF β-1 signalling is a SMAD3- dependent pathway. SET9 is a methyltransferase enzyme that can methylate non-histone protein substrates including the transcription factors p53, Stat3, Rb, TAF10, E2F1, ERα, NF-κB, and DNMT1. I show that SET9 plays a central role in regulating SMAD3 activity, as shown by SET9 knockdown. I also show that wild type SET9 overexpression results in increased SMAD3 activity, in the presence of TGF β-1. Conversely, expression of a mutant SET9, which lacks methyltransferase activity, 15 failed to increase SMAD3 activity, even in the presence of TGF β-1. Furthermore, SET9 gene silencing with siRNAs significantly attenuated TGF β-1-induced ECM gene expression. These novel effects of SET9 warrant further evaluation of SET9 as a target in the treatment of fibrotic diseases such as CKD. Screening a demethylase siRNA library showed that the putative demethylase HSPBAP-1 is also involved in TGF β/SMAD signalling. Interestingly, I show that HSPBAP-1 interacts with SMAD3, and suppresses the transcriptional activity of SMAD3-driven reporter-genes. This is the first report of such an interaction, and the first data implicating a potential demethylation event in TGF β-1/SMAD3 signalling. Taken together, the work in this study defines novel roles of SET9 and HSPBAP-1 in fibrosis by mediating TGF β-1/SMAD3 signalling. On the basis of my work, future examination of SET9/HSPBAP-1 in whole organism models of renal fibrosis should be considered.

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15

Matin, Maryam Moghaddam. "Analysis and applications of mutant C5-DNA methyltransferases." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.673841.

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16

Alenad, Amal. "The role of DNA methyltransferases in fetal programming." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/338966/.

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Human epidemiological and experimental animal studies show that a poor intra-uterine environment induced by restricted maternal diet during pregnancy leads to persistent alterations in the metabolism and physiology of the offspring and an altered susceptibility to chronic disease in adult life such as cardiovascular disease and metabolic syndrome. This phenomenon has been termed fetal programming. In rats, maternal protein restriction (MPR) during pregnancy alters the expression of specific genes involved in lipid and carbohydrate homeostasis such as glucocorticoid receptor (GR) and peroxisomal proliferator-activated receptor–alpha (PPARα). Evidence is accumulating which indicates that persistent changes in the expression of GR and PPARα are mediated by changes in the epigenetic regulation of these genes within the offspring. Epigenetics refers to processes that stably alter gene activity without altering DNA sequence. DNA methylation and histone modification are the most significant epigenetic modifications. However the mechanism by which alterations in maternal diet can induce the altered epigenetic regulation of genes such as GR or PPARα is currently unknown. The aim therefore of this project was to investigate the role of the DNA methyltransferase1 (Dnmt1). Dnmt1 is essential for the maintenance of DNA methylation patterns in the induction of the altered epigenetic regulation of genes in response to maternal diet. We initially investigated the effect of MPR on Dnmt1 mRNA expression in heart, brain and spleen from control and protein restriction (PR) offspring on PN34. We found that MPR altered the expression of Dnmt1 and the de novo DNA methyltransferases Dnmt3a, and 3b in a tissue specific manner. The effect of MPR on the expression and methylation of GR and PPARα was also tissue specific. However, in most tissues examined there was not a simple inverse relationship between GR or PPARα expression and methylation or with levels of Dnmt1 expression. To assess how widespread the changes in gene expression induced by MPR are, microarray analysis was conducted in E8 embryos from control and PR fed dams and results were validated by RT-PCR. Results showed that only relatively small subsets of genes were affected by MPR or global dietary restriction (UN). Gene ontology analysis also revealed that similar pathways were altered under condition of both maternal PR and UN and interestingly one of the pathways altered by both maternal PR and UN was chromatin modification. In both PR and UN embryos on E8 a decrease in Dnmt1, Dnmt3a and 3b expression was observed as well as a decrease in the histone methyltransferases EZH2, Suv39H1 and the HDAC Sirt1 in the embryos from PR dams compared to controls. Alterations in the expression of the DNA and histone methyltransferases in response to MPR were accompanied by changes in DNA methylation and histone modification at the GR promoter as early as E14.

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Peng, Yi. "Structural Studies of the S-Adenosylmethionine-Dependent Methyltransferases." Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1228316254.

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Ragamustari, Safendrri Komara. "Characterization of O-methyltransferases involved in lignan biosynthesis." Kyoto University, 2014. http://hdl.handle.net/2433/188774.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第18336号
農博第2061号
新制||農||1023(附属図書館)
学位論文||H26||N4843(農学部図書室)
31194
京都大学大学院農学研究科応用生命科学専攻
(主査)教授梅澤俊明, 教授矢﨑一史, 教授三上文三
学位規則第4条第1項該当

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Sayegh, Joyce Ellen. "Identification and characterization of eukaryotic protein arginine methyltransferases." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1495958991&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Ridgway, Neale David. "Rat hepatic phosphatidylethanolamine N-methyltransferase : enzyme purification and characterization." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29377.

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Phosphatidylethanolamine (PE) N-methyltransferase catalyzes the stepwise transfer of methyl groups from S-adenosyl-L-methionine (AdoMet) to the amino headgroup of PE. Successive methylation results in the formation of the two intermediates, phosphatidyl-N-monomethylethanolamine (PMME) and phosphatidyl-N, N-dimethylethanolamine (PDME), and the final product phosphatidylcholine (PC). PE N-methyltransferase is an integral membrane protein localized primarily in the endoplasmic reticulum (microsomal fraction) of liver. PE-, PMME- and PDME-dependent PE N-methyltransferase activities were purified from Triton X-100 solubilized microsomes 429-, 1542- and 832-fold, respectively. The purified enzyme was composed of a single 18.3 kDal protein as determined by SDS-PAGE. Molecular mass analysis of purified PE N-methyltransferase (in Triton X-100 micelles) by gel filtration on Sephacryl S-300 indicated the enzyme existed as a 24.7 kDal monomer. PE N-methyltransferase catalyzed the complete conversion of PE to PC and had a pH optimum of 10 for all three steps. A Triton X-100 mixed micelle assay was developed to assay PE-, PMME- and PDME-dependent activities of both pure and microsomal PE N-methyltransferase. The AT-terminal amino acid sequence of rat liver PE N-methyltransferase and the recently cloned 23.1 kDal S. cerevisiae PEM 2 were found to be 35% homologous. Double reciprocal plots for PE N-methyltransferase at fixed Triton X-100 concentrations and increasing PE, PMME or PDME were highly cooperative. Similar cooperative effects were noted when phospholipid was fixed and Triton X-100 increased. The cooperativity could be partially abolished if a fixed mol% of nonsubstrate phospholipid such as PC was included in the assay. This would indicate that PE N-methyltransferase has specific binding requirements for a site(s) in contact with the micellar substrate. The occupation of this boundary layer by phospholipid is essential for full expression of enzyme activity. Kinetic analysis revealed that PMME and PDME methylation followed an ordered Bi-Bi mechanism. The overall mechanism involves initial binding of PE to a common site and successive methylation steps involving the binding and release of AdoMet and S-adenosyl-L-homocysteine, respectively. Cysteine residue(s) (which are rapidly oxidized in the absence of reduced thiols) are involved in the catalytic mechanism. Reverse-phase HPLC was used to fractionate the phospholipid products of PE N-methyltransferase into individual molecular species. Substrate specificity experiments on PE N-methyltransferase in vitro and in vivo revealed no selectivity for any molecular species of diacyl PE, PMME or PDME. The PE-derived PC, which is rich in 16:0-22:6, is rapidly remodeled to conform to the molecular species compositon of total hepatocyte PC in vivo . The 18.3 kDal PE N-methyltransferase was found to be a substrate for cAMP-dependent protein kinase in vitro. However, only 0.25 mol phosphorus/mol of PE Af-methyltransferase was incorporated, with no observed effect on activity. Studies on PE N-methyltransferase regulation in choline-deficient rat liver indicated that activity changes were due to elevated levels of cellular PE. Immunoblotting of choline-deficient liver microsomes or hepatocyte membranes with a anti-PE N-methyltransferase antibody revealed no alteration in enzyme mass. While more work is needed, initial indications are that hepatic PE N-methyltransferase is a constitutive enzyme regulated primarily by substrate and product levels.
Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate

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Lindqvist, Malin. "Pharmacogenetic studies of thiopurines : focus on thiopurine methyltransferase /." Linköping : Linköpings universitet, 2005. http://www.bibl.liu.se/liupubl/disp/disp2005/med893s.pdf.

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22

Rebelo, Adriana. "Probing Mitochondrial DNA Structure with Mitochondria-Targeted DNA Methyltransferases." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/344.

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The mitochondria contain their own genome, which is organized in a dynamic high-order nucleoid structure consisting of several copies of mitochondrial DNA (mtDNA) molecules associated with proteins. The mitochondrial nucleoids are the units of mtDNA inheritance, and are the sites of mtDNA transcription, replication and maintenance. Therefore, the integrity of mitochondrial nucleoids is a key determinant of mitochondrial metabolism and the bioenergetic state of the cell. Deciphering the interaction of mtDNA with proteins in nucleoprotein complexes is fundamental to understand the mechanisms of mtDNA segregation leading to mitochondrial dysfunction and to develop therapies to treat diseases associated with mtDNA mutations. The work presented in this dissertation provides essential insights into the dynamics of mtDNA interaction with nucleoid proteins. In order to unveil the organization of the mitochondrial genome, we have mapped major regulatory regions of the mtDNA in vivo using mitochondrial-targeted DNA methyltransferases. In chapter 2, we have demonstrated that DNA methyltranferases are powerful tools in probing mtDNA-protein interactions in living cells. The DNA methyltransferases' accessibility to their cognate sites in the mtDNA is negatively correlated with the frequency and binding strength that protein factors occupy a specific site. Our results show that the transcription termination region (TERM) within the tRNALeu(UUR) gene is consistently and strongly protected from methylation, suggesting frequent and high affinity binding of mTERF1 (mitochondrial transcription termination factor 1). DNA methyltransferases have also been shown to be effective in detecting changes in mitochondrial nucleoid architecture due to nucleoid remodeling. We were able to determine changes in the packaging state of mitochondrial nucleoids by monitoring changes in mtDNA accessibility. The impact of altered levels of major nucleoid proteins was assessed by monitoring changes in mtDNA methylation pattern. We observed a more condensed nucleoid state causing a decrease in mtDNA methylation when the levels of the mitochondrial transcription factor A (TFAM) were altered. Changes in mtDNA methylation pattern were also evident when cells were treated with ethidium bromide (EtBr) and hydrogen peroxide. The mtDNA nucleoids adopted a less compact state during rapid mtDNA replication after EtBr treatment. In contrast, we observed a more compact mtDNA, less accessible to DNA methyltransferase after hydrogen peroxide treatment. Our results indicate that mitochondrial nucleoids are not static, but are constantly been modulated in response to factors that affect the nucleoid environment. In chapter 3, we identified the in vivo DNA binding sites of major transcription regulatory proteins, TFAM and mTERF3 using a targeted gene methylation (TAGM) strategy. In this approach, the mtDNA binding protein is fused to a DNA methyltransferase as an attempt to selectively methylate the sites adjacent to the protein target DNA region. Knowledge on how proteins interact with the mtDNA in high-order structures, which function as a mitochondrial genetic unit, will help elucidate the segregation and accumulation of mutated mtDNA in diseased tissues.

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Genger, Ruth Kathleen, and Ruth Genger@csiro au. "Cytosine methylation, methyltransferases and flowering time in Arabidopsis thaliana." The Australian National University. Faculty of Science, 2000. http://thesis.anu.edu.au./public/adt-ANU20011127.115231.

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Environmental signals such as photoperiod and temperature provide plants with seasonal information, allowing them to time flowering to occur in favourable conditions. Most ecotypes of the model plant Arabidopsis thaliana flower earlier in long photoperiods and after prolonged exposure to cold (vernalization). The vernalized state is stable through mitosis, but is not transmitted to progeny, suggesting that the vernalization signal may be transmitted via a modification of DNA such as cytosine methylation. The role of methylation in the vernalization response is investigated in this thesis. ¶ Arabidopsis plants transformed with an antisense construct to the cytosine methyltransferase METI (AMT) showed significant decreases in methylation. AMT plants flowered significantly earlier than unvernalized wildtype plants, and the promotion of flowering correlated with the extent of demethylation. The flowering time of mutants with decreased DNA methylation (ddm1) was promoted only in growth conditions in which wildtype plants showed a vernalization response, suggesting that the early flowering response to demethylation operated specifically through the vernalization pathway. ¶ The AMT construct was crossed into two late flowering mutants that differed in vernalization responsiveness. Demethylation promoted flowering of the vernalization responsive mutant fca, but not of the fe mutant, which has only a slight vernalization response. This supports the hypothesis that demethylation is a step in the vernalization pathway. ¶ The role of gibberellic acid (GA) in the early flowering response to demethylation was investigated by observing the effect of the gai mutation, which disrupts the GA signal transduction pathway, on flowering time in plants with demethylated DNA. The presence of a single gai allele delayed flowering, suggesting that the early flowering response to demethylation requires a functional GA signal transduction pathway, and that demethylation increases GA levels or responses, directly or indirectly. ¶ In most transgenic lines, AMT-mediated demethylation did not fully substitute for vernalization. This indicates that part of the response is not affected by METI-mediated methylation, and may involve a second methyltransferase or a factor other than methylation. A second Arabidopsis methyltransferase, METIIa, was characterized and compared to METI. The two genes are very similar throughout the coding region, and share the location of their eleven introns, indicating that they diverged relatively recently. Both are transcribed in all tissues and at all developmental stages assayed, but the level of expression of METI is significantly higher than that of METIIa. The possible functions of METI, METIIa, and other Arabidopsis cytosine methyltransferase genes recently identified are discussed.

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24

Alfageih, Laila Mohamed. "Biochemical and genetic studies of bacterial C5-DNA methyltransferases." Thesis, University of Sheffield, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548643.

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25

Cohen, H. "Investigating and engineering the substrate specificity of DNA methyltransferases." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597811.

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DNA methyltransferases catalyse the transfer of methyl groups from the cofactor S-adenosyl-L-methionine to a target base (adenine or cytosine) within a cognate recognition sequence. I have studied cofactor binding, DNA specificity and the role of conserved amino acid motifs in the cytosine C⁵ methyltransferase M.HaeIII. By measuring the competitive inhibition of methylation by a series of cofactor analogues, each modified at a single position, the importance of each functional group for cofactor binding to M.HaeIII was probed. The functional significance of amino-acid residues in M.HaeIII was investigated using in vitro compartmentalisation (IVC), an activity-based selection method. IVC was used to obtain active variants of M.HaeIII from libraries diversified at conserved motifs in the catalytic and DNA binding domains. M.HaeIII modifies the central cytosine of the sequence (5’-GGCC-3’). Using bisulphite sequencing, cytosines in a variety of other sequence contexts were found to be methylated at lower levels by M.HaeIII both in vivo and in vitro. IVC was then used to select mutant enzymes with an improved ability to methylate the non-canonical site AGCC.

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Mathers, Lucille Sarah. "The role of DNA methyltransferases in plant genomic imprinting." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512263.

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Genomic imprinting is the epigenetic modification of loci, primarily by DNA methylation, which results in parent-of-origin-specific monoallelic expression of a small subset of genes. In plants, imprinting occurs during endosperm development and a balance of maternally- and paternally-expressed imprinted genes is essential for normal seed development. Dependence on DNA methylation for imprinting highlights the potential to manipulate seed development, and consequently seed size, by altering DNA methyltransferase activity. DNA METHYLTRANSFERASE 1 (MET1) is the primary plant maintenance DNA methyltransferase and plays a significant role in imprinting. However, no evaluation of the potential role for other MET1 family members in genomic imprinting has been reported. The current model for the control of imprinting in plants suggests that maintenance DNA methyltransferases are required throughout development, yet the tissue-specific requirement of these enzymes is unconfirmed as analysis has relied solely on constitutive DNA methyltransferase mutants. To address these problems and to evaluate the potential to alter seed size, the work reported in this thesis investigated the potential involvement of putative maintenance DNA methyltransferases MET2a, MET2b and MET3 and the tissue-specific role of MET1 in imprinting. Imprinting was not significantly altered in met2a-1, met2b-1 and met3-1 mutants, indicating that MET1 is the sole DNA methyltransferase required for imprinting. Transcriptional analysis suggested MET1 is expressed throughout floral organ development and in the male and female gametophyte generation indicating that MET1 is potentially available to maintain imprinting-dependent methylation in these tissues. Tools to suppress MET1 tissuespecifically were developed to investigate the tissue-specific requirement of MET1 for imprinting. Analysis indicates that such tools could also be used to alter seed size by manipulating imprinting in commercially important species. Further work is needed to validate this approach.

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Lee, Angelina Huai-Lo. "The role of O-methyltransferases in antibiotic polyketide biosynthesis." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620640.

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28

Somme, Jonathan. "Structure-function relationship studies on the tRNA methyltransferases TrmJ and Trm10 belonging to the SPOUT superfamily." Doctoral thesis, Universite Libre de Bruxelles, 2015. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209122.

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During translation, the transfer RNAs (tRNAs) play the crucial role of adaptors between the messenger RNA and the amino acids. The tRNAs are first transcribed as pre-tRNAs which are then maturated. During this maturation, several nucleosides are modified by tRNA modification enzymes. These modifications are important for the functions of the tRNAs and for their correct folding. Many of the modifications are methylations of the bases or the ribose. Four families of tRNA methyltransferases are known, among which the SPOUT superfamily. Proteins of this superfamily are characterised by a C-terminal topological knot where the methyl donor is bound. With the exception of the monomeric Trm10, all known SPOUT proteins are dimeric and have an active site composed of residues of both protomers. Interestingly, depending on the organism, the same modification can be catalysed by completely unrelated enzymes. On the other hand, homologous enzymes can have different specificities or/and activities. These differences are well illustrated for the TrmJ and Trm10 enzymes.

In the first part of this work we have identified the TrmJ enzyme of Sulfolobus acidocaldarius (the model organism of hyperthermophilic Crenarchaeota) which 2’-O-methylates the nucleoside at position 32 of tRNAs. This protein belongs to the SPOUT superfamily and is homologous to TrmJ of the bacterium Escherichia coli. A comparative study shows that the two enzymes have different specificities for the nature of the nucleoside at position 32 as well as for their tRNA substrates. To try to understand these shifts of specificity at a molecular level we solved the crystal structure of the SPOUT domains of the two TrmJ proteins.

In the second part of this work, we have determined the crystal structure of the Trm10 protein of S. acidocaldarius. This is the first structure of a 1-methyladenosine (m1A) specific Trm10 and also the first structure of a full length Trm10 protein. The Trm10 protein of S. acidocaldarius is distantly related to its yeast homologues which are 1-methylguanosine (m1G) specific. To understand the difference of activity between the Trm10 enzymes, we compared the yeast and the S. acidocaldarius Trm10 structures. Remarkably several Trm10 proteins (such as Trm10 of Thermococcus kodakaraensis) are even able to form both m1A and m1G. To understand the capacity of the T. kodakaraensis protein to methylate A and G, a mutational study was initiated./Lors de la traduction, les ARN de transfert (ARNt) jouent le rôle crucial d’adaptateurs entre l’ARN messager et les acides aminés. Les ARNt sont transcrits sous forme de pré-ARNt qui doivent être maturés. Lors de cette maturation, plusieurs nucléosides sont modifiés. Un grand nombre de ces modifications sont des méthylations des bases ou du ribose. Quatre familles d’ARNt méthyltransferases sont actuellement connues, dont la superfamille des SPOUT. Les membres de cette superfamille sont caractérisés par un nœud dans la chaîne polypeptidique du côté C-terminal. C’est au niveau de ce nœud que se lie la S-adénosylméthionine qui est le donneur de groupement méthyle. A l’exception de Trm10 qui est monomérique, toutes les protéines SPOUT connues sont dimériques et leur site actif est formé de résidus provenant des deux protomères. Selon l’espèce, une même modification peut être formée à la même position dans la molécule d’ARNt par des enzymes qui appartiennent à des familles différentes. A l’opposé, des enzymes homologues peuvent présenter des spécificités ou des activités différentes.

Au cours de ce travail, nous avons identifié l’enzyme TrmJ de Sulfolobus acidocaldarius (l’organisme modèle des Crénarchées hyperthermophiles) qui méthyle le ribose du nucléoside en position 32 des ARNt. Cette protéine est un homologue de l’enzyme TrmJ de la bactérie Escherichia coli. L’étude comparative que nous avons réalisée a révélé que ces deux enzymes présentent une différence de spécificité pour la nature du nucléoside en position 32 ainsi que pour les ARNt substrats. Afin de comprendre ces différences de spécificité au niveau moléculaire, les structures des domaines SPOUT des deux TrmJ ont été déterminées et comparées.

En parallèle, nous avons résolu la structure cristalline de la protéine Trm10 de S. acidocaldarius. C’est la première structure disponible d’un enzyme Trm10 formant de la 1-méthyladénosine (m1A). C’est aussi la première structure complète d’une protéine Trm10. Les enzymes homologues des levures Saccharomyces cerevisiae et Schizosaccharomyces pombe qui n’ont que peu d’identité de séquence avec l’enzyme de S. acidocaldarius, forment de la 1-méthylguanosine (m1G). Dans le but de comprendre comment ces enzymes homologues peuvent présenter des activités différentes, leurs structures ont été comparées. De manière surprenante, certains homologues de Trm10 (comme l’enzyme de l’Euryarchée Thermococcus kodakaraensis) sont capables de former du m1A et du m1G. Afin de mieux comprendre comment ces protéines sont capables de méthyler deux types de bases, nous avons initié l’étude de l’enzyme Trm10 de T. kodakaraensis par mutagenèse dirigée.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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29

Xie, Tao. "A structural and functional study of human catechol-o-methyltransferase gene in Parkinson's disease /." Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20667620.

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30

Latham, Tom. "De novo methyltransferases, DNA methylation and cancer : a transgenic model." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/24811.

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One of the most important controversies in the field of cancer epigenetics is the question of whether aberrant CpG island methylation of tumour suppressor genes can cause cancer or whether such abnormalities of DNA methylation are secondary to the malignant process. We address this question by prospectively causing abnormal methylation events in vivo. We have produced transgenic mice which over-express the de novo methyltransferase Dnmt3b under the widely expressed CAG promoter. Tg(Dnmt3b)+mice develop normally and are fertile, but die at 4-5 months, developing dilated cardiomyopathy. CpG island methylation is globally increased, and abnormal methylation of specific genes, including the tumour suppressor genes Cdkn1a, Cdkna2a and Hic1 is detectable. However, there is no spontaneous cancer incidence. Crossing the mice with the intestinal tumour prone Apc^+/-min mice leads to a modest increase in polyp number and the frequency of dysplastic tumours, although methylation of the Apc gene is not detectable in normal mucosa from Dnmt3b overexpressing mice, and methylation of the Apc promoter occurs with equal frequency in microdissected tumours from Apc^+/- mice regardless of Tg(Dnmt3b)+ genotype. The results show that increases of methylation can be well tolerated, suggesting that although methylation can be increased, active silencing by methylation is more unusual. In particular, the active silencing of tumour suppressor genes by de novo methylation is unlikely to be a primary event in the formation of tumours, although it may play a role in modulating tumour progression.

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Dukhyil, Abdul Aziz Abdullah Bin. "Investigations of error-prone repair using mutant bacterial DNA methyltransferases." Thesis, University of Sheffield, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312811.

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32

Anthony, Shelagh. "Analysis of mammalian protein arginine N-methyltransferases in the vasculature." Thesis, University College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424909.

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Lee, Yin Fai. "In vitro evolution of enzymes : selecting DNA cytosine-5 methyltransferases." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621227.

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Varney, Amy. "Small molecule inhibitors and substrate analyses of protein arginine methyltransferases." Thesis, University of Oxford, 2015. https://ora.ox.ac.uk/objects/uuid:58350487-397d-4fa7-a545-429b16d23540.

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Chapter 1 introduces the Protein Arginine Methyltransferases (PRMTs) as epigenetic regulators that decorate peptidic arginine with methyl groups. Evidence for PRMT involvement in cancer pathogenesis is reviewed and their plausibility as therapeutic targets is introduced. The methylation patterns conferred by the PRMTs is described, and the existence of novel patterns is considered. Techniques for assaying PRMT activity are compared and contrasted and a discussion of current PRMT inhibitors is presented. The chapter concludes by outlining the aims of the thesis. Chapter 2 describes synthesis towards novel methylated arginine molecules that are fully protected for inclusion in peptides via solid phase peptide synthesis. Chapter 3 outlines the total synthesis of protected d-monomethylated arginine for peptide synthesis. This methylation pattern is known in yeast but has not yet been identified in humans. Chapter 4 details a new mass spectrometry-based assay that can be applied for inhibitor and substrate analyses. Synthesis of a novel histone peptide containing the d-monomethylated arginine, produced in Chapter 3, is also described and this is tested for relevance as a human epigenetic marker. Novel polymethylation patterns are also explored in a total of five histone peptides. This chapter concludes with discussion of possible methylation pattern rearrangements. Chapter 5 describes the synthesis and testing of two series of putative PRMT inhibitors based on previously identified scaffolds within this research group. Data obtained from three different assays, including that outlined in Chapter 4, are analysed and suggestions as to the direction of PRMT assay design are offered. Chapter 6 provides the experimental data to support Chapters 2-5, including all organic synthesis procedures, protein & peptide syntheses and assay methodology.

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35

Duygu, Koca [Verfasser], and Roland [Akademischer Betreuer] Schüle. "Characterization of novel histone methyltransferases and their roles in cancer." Freiburg : Universität, 2019. http://d-nb.info/1206095741/34.

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Morettin, Alan James. "Investigating the Role of Protein Arginine Methyltransferases in Breast Cancer Etiology." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/31920.

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Breast cancer is the most commonly diagnosed cancer amongst Canadian women. Though numerous treatments are available, in many instances tumours become refractory or recur. Therefore, understanding the biological events that lead to the progression and therapeutic resistance of breast cancer is essential for the development of novel treatment options for this disease. Numerous members of the protein arginine methyltransferase (PRMT) family, which are the enzymes responsible for catalyzing methylation on arginine residues are aberrantly regulated in breast cancer. Hence, understanding the precise contribution of PRMTs to the development and progression of breast cancer is important. This Thesis will present my findings on the alternatively spliced PRMT1 isoform, PRMT1v2, previously identified to be overexpressed in breast cancer cell lines and here shown to promote breast cancer cell survival and invasion. Second, a novel role is ascribed to PRMT6, another PRMT aberrantly expressed in breast cancer. PRMT6 promotes chemoresistance to the drug bortezomib by mediating stress granule formation through down-regulation of eIF4E. Increased stress granule formation in bortezomib-resistant cancer cells promotes cell survival. Third, DDX3, a prototypical PRMT substrate which is overexpressed in breast cancer cell lines and stimulates transformation of mammary epithelial cells is a novel substrate of PRMT1, CARM1, and PRMT6. Lastly, TDRD3, a reader/effector of arginine methylation also overexpressed in breast tumours regulates breast cancer cell proliferation, anchorage-independent growth and cell motility and invasion.

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Weirich, Sara [Verfasser], and Albert [Akademischer Betreuer] Jeltsch. "Enzymatic characterization of protein lysine methyltransferases / Sara Weirich ; Betreuer: Albert Jeltsch." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2017. http://d-nb.info/1139256068/34.

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38

Tomkuvienė, Miglė. "Methyltransferases as tools for sequence-specific labeling of RNA and DNA." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2013~D_20131209_091531-59976.

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Investigation of RNA and DNA function often requires sequence-specific incorporation of various reporter and affinity probes. This can be achieved using AdoMet-dependent methyltransferases (MTases) as they can be active with synthetic AdoMet analogues equipped with transferable chains larger than the methyl group. These chains usually carry reactive groups that can be further chemically appended with required reporters. For this, azide-alkyne 1,3-cycloaddition (AAC), also called “click”, reaction is particularly attractive. This work shows that the HhaI cytosine-5 DNA MTase (variant Q82A/Y254S/N204A) catalyzes efficient sequence-specific transfer of hex-2-ynyl side chains containing terminal alkyne or azide groups from synthetic cofactor analogues to DNA. Both the enzymatic transfer and subsequent “click” coupling of a fluorophore can be performed even in cell lysates. For RNA labeling, the activity of an archaeal RNA 2‘-O-MTase C/D ribonucleoprotein complex (RNP) with synthetic cofactors was investigated. It was shown that synthetically reprogrammed guide RNA sequences can be used to direct the C/D RNP-dependent transfer of a prop-2-ynyl group to predetermined nucleotides in substrate RNAs. Followed by AAC this can be used for programmable sequence-specific labeling of a variety of RNA substrates in vitro. These new possibilities for specific labeling of nucleic acids can be adopted in biochemistry, biomedical, nanotechnology, etc. research.
Tiriant DNR ir RNR, neretai svarbu prijungti įvairius reporterinius ar giminingumo žymenis griežtai apibrėžtose (sekos) vietose – t.y. specifiškai. Tam galima pasitelkti fermentus metiltransferazes (MTazes). Natūraliai jos naudoja kofaktorių AdoMet, tačiau gali būti aktyvios ir su sintetiniais jo analogais, turinčiais ilgesnes nei metil- pernešamas grandines. Jei šios grandinės turi galines funkcines grupes, prie jų vėliau cheminių reakcijų pagalba galima prijungti norimus žymenis. Tam itin patogi azidų-alkinų cikloprijungimo (AAC), dar vadinama „click“, reakcija. Šiame darbe parodyta, kad DNR citozino-5 MTazė HhaI (variantas Q82A/Y254S/N204A) efektyviai katalizuoja sekai specifinę heks-2-inil- grandinių, turinčių galines alkinil- arba azido- grupes, pernašą nuo sintetinių kofaktorių ant DNR. Naudojant šią MTazės-kofaktorių sistemą bei AAC, visą specifinio DNR žymėjimo procesą galima atlikti netgi ląstelių lizate. RNR žymėjimui ištirtas archėjų RNR 2‘-O-MTazės C/D ribonukleoproteininio komplekso aktyvumas su sintetiniais kofaktoriais. Parodyta galimybė sintetiškai keičiant kreipiančiąją RNR, prop-2-inilgrupės pernašą nukreipti į norimas įvairių substratinių RNR sekos vietas ir po to AAC reakcijos pagalba prijungti fluoroforą. Taigi, sukurtas naujas molekulinis įrankis, leidžiantis be suvaržymų pasirinkti norimą pažymėti RNR seką. Šios naujos specifinio nukleorūgščių žymėjimo galimybės gali būti pritaikytos biochemijos, biomedicinos, nanotechnologijų ir kitose tyrimų srityse... [toliau žr. visą tekstą]

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Raafiq, Qazi Muhammad [Verfasser]. "Investigation of the specificity of protein lysine methyltransferases / Qazi Muhammad Raafiq." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2013. http://d-nb.info/1037012887/34.

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40

Willcock, Damion F. "A mutational analysis of motifs in EcoKI common to adenine methyltransferases." Thesis, University of Edinburgh, 1994. http://hdl.handle.net/1842/11580.

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Type 1 restriction/modification systems are complex multifunctional enzymes comprising three polypeptides, Hsd R, M and S. All three polypeptides are required to form a restriction enzyme but M and S alone are sufficient to form an N6 adenine methyltransferase. The Hsd M polypeptide of the type I system Eco K contains motifs characteristic of N6 adenine methyltransferases (Asn/Asp Pro Pro Phe/Tyr) and of methyltransferases in general (Phe X Gly X Gly). These motifs may identify amino acid sequences critical to methyltransferase function. This work describes an in vivo and in vitro analysis of site directed mutations within these two motifs and is the first report of such changes within a type I system. Biochemical analysis identifies the Asn/Asp Pro Pro Phe/Tyr region as critical to catalysis and in close proximity to the S-adenosylmethionine binding site. Mutations which remain within the overall consensus do not necessarily retain activity and hence indicate a degree of stringency associated with this motif. A mutation within the Phe X Gly X Gly motif abolishes SAM binding but retains DNA binding activity. In addition this mutant is temperature sensitive.

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Picking, Jonathan William. "Glycine Betaine and Proline Betaine Specific Methyltransferases of the MttB Superfamily." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563468258124346.

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42

Galloway, Summer E. "Functional characterization of conserved domains within the L protein component of the vesicular stomatitis virus RNA-dependent RNA polymerase implications for transcription and MRNA processing /." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2008. https://www.mhsl.uab.edu/dt/2010r/galloway.pdf.

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43

Holford, Kenneth C. Borst David Wellington. "Molecular characterization of farnesoic acid o-methyl transferase in the American lobster (Homarus americanus)." Normal, Ill. Illinois State University, 2000. http://wwwlib.umi.com/cr/ilstu/fullcit?p9986727.

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Thesis (Ph. D.)--Illinois State University, 2000.
Title from title page screen, viewed May 11, 2006. Dissertation Committee: David Borst (chair), Anthony Otsuka, Radheshyam Jayaswal, Paul Garris, David Williams. Includes bibliographical references (leaves 130-135) and abstract. Also available in print.

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44

Zhang, Li. "DRMT4 (Drosophila arginine methyltransferase 4) : functions in Drosophila oogenesis." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80905.

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DRMT4 (Drosophila Arginine MethylTransferase 4) is an arginine methyltransferase in Drosophila (Boulanger et al. 2004). It shows the highest identities with mammalian PRMT4/CARM1 (Protein Arginine MethylTransferase 4) (59% identity, 75% similarity). HPLC analysis demonstrated that DRMT4 belongs to the type I class of methyltransferases (Boulanger et al. 2004), meaning that DRMT4 catalyzes asymmetrical dimethylarginine formation. A polyclonal antibody against DRMT4 was generated and used to study DRMT4 expression using western blots and immunostainings. In order to study DRMT4 function in Drosophila using genetic methods, we created three kinds of DRMT4 transgenes: a genomic DRMT4 under its own control, a genomic DRMT4-GFP fusion gene and a cDNA DRMT4 under UAS control. We investigated DRMT4 localization in wild type flies using the DRMT4-GFP transgenic line and immunostaining.

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45

Xie, Tao, and 謝濤. "A structural and functional study of human catechol-o-methyltransferase gene in Parkinson's disease." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239535.

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46

Schroeder, Steven Gerard. "Structure-function studies of lima bean trypsin inhibitor and EcoRII methyltransferase /." free to MU campus, to others for purchase, 2000. http://wwwlib.umi.com/cr/mo/fullcit?p9974684.

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47

Reuben, Melanie. "Characterization of mutant N², N²-dimethylguanosine-specific tRNA methyltransferases from Saccharomyces cerevisiae." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25984.pdf.

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48

Alazizi, Adnan. "Molecular Cloning, Expression, purification and Characterization of the Zebrafish Catechol-O-methyltransferases." University of Toledo Health Science Campus / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=mco1303391786.

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Dobrowolski, Curtis Noel. "HISTONE LYSINE METHYLTRANSFERASES SELECTIVELY RESTRICT HIV-1 IN CENTRAL MEMORY T-CELLS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522842870401743.

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Zamudio, Jesse Ray. "Identification of SL RNA cap 2' -O-ribose methyltransferases in Trypanosoma brucei." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1779835201&sid=12&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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Dissertations / Theses on the topic 'Methyltransferases'

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