- DNA methyltransferase
N-6 DNA Methylase crystal structure of type i restriction enzyme ecoki m protein (ec 18.104.22.168) (m.ecoki) Identifiers Symbol N6_Mtase Pfam PF02384 Pfam clan CL0063 InterPro IPR003356 PROSITE PDOC00087 Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary HsdM N-terminal domain Identifiers Symbol HsdM_N Pfam PF12161 Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary C-5 cytosine-specific DNA methylase structure of human dnmt2, an enigmatic dna methyltransferase homologue Identifiers Symbol DNA_methylase Pfam PF00145 Pfam clan CL0063 InterPro IPR001525 PROSITE PDOC00089 SCOP 1hmy Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary DNA methylase crystal structure of methyltransferase mboiia (moraxella bovis) Identifiers Symbol N6_N4_Mtase Pfam PF01555 Pfam clan CL0063 InterPro IPR002941 PROSITE PDOC00088 SCOP 1boo Available protein structures: Pfam structures PDB RCSB PDB; PDBe PDBsum structure summary
In biochemistry, the DNA methyltransferase (DNA MTase) family of enzymes catalyze the transfer of a methyl group to DNA. DNA methylation serves a wide variety of biological functions. All the known DNA methyltransferases use S-adenosyl methionine (SAM) as the methyl donor.
MTases can be divided into three different groups on the basis of the chemical reactions they catalyze:
- m6A - those that generate N6-methyladenine EC 22.214.171.124
- m4C - those that generate N4-methylcytosine EC 126.96.36.199
- m5C - those that generate C5-methylcytosine EC 188.8.131.52
m6A and m4C methyltransferases are found primarily in prokaryotes. m5C methyltransfereases are found in some lower eukaryotes, in most higher plants, and in animals beginning with the echinoderms.
m6A methyltransferases (N-6 adenine-specific DNA methylase) (A-Mtase) are enzymes that specifically methylate the amino group at the C-6 position of adenines in DNA. They are found in the three existing types of bacterial restriction-modification systems (in type I system the A-Mtase is the product of the hsdM gene, and in type III it is the product of the mod gene). These enzymes are responsible for the methylation of specific DNA sequences in order to prevent the host from digesting its own genome via its restriction enzymes. These methylases have the same sequence specificity as their corresponding restriction enzymes. These enzymes contain a conserved motif Asp/Asn-Pro-Pro-Tyr/Phe in their N-terminal section, this conserved region could be involved in substrate binding or in the catalytic activity. The structure of N6-MTase TaqI (M.TaqI) has been resolved to 2.4 A. The molecule folds into 2 domains, an N-terminal catalytic domain, which contains the catalytic and cofactor binding sites, and comprises a central 9-stranded beta-sheet, surrounded by 5 helices; and a C-terminal DNA recognition domain, which is formed by 4 small beta-sheets and 8 alpha-helices. The N- and C-terminal domains form a cleft that accommodates the DNA substrate. A classification of N-MTases has been proposed, based on conserved motif (CM) arrangements. According to this classification, N6-MTases that have a DPPY motif (CM II) occurring after the FxGxG motif (CM I) are designated D12 class N6-adenine MTases. The type I restriction and modification system is composed of three polypeptides R, M and S. The M (hsdM) and S subunits together form a methyltransferase that methylates two adenine residues in complementary strands of a bipartite DNA recognition sequence. In the presence of the R subunit, the complex can also act as an endonuclease, binding to the same target sequence but cutting the DNA some distance from this site. Whether the DNA is cut or modified depends on the methylation state of the target sequence. When the target site is unmodified, the DNA is cut. When the target site is hemimethylated, the complex acts as a maintenance methyltransferase, modifying the DNA so that both strands become methylated. hsdM contains an alpha-helical domain at the N-terminus, the HsdM N-terminal domain.
m4C methyltransferases (N-4 cytosine-specific DNA methylases) are enzymes that specifically methylate the amino group at the C-4 position of cytosines in DNA. Such enzymes are found as components of type II restriction-modification systems in prokaryotes. Such enzymes recognise a specific sequence in DNA and methylate a cytosine in that sequence. By this action they protect DNA from cleavage by type II restriction enzymes that recognise the same sequence
m5C methyltransferases (C-5 cytosine-specific DNA methylase) (C5 Mtase) are enzymes that specifically methylate the C-5 carbon of cytosines in DNA to produce C5-methylcytosine. In mammalian cells, cytosine-specific methyltransferases methylate certain CpG sequences, which are believed to modulate gene expression and cell differentiation. In bacteria, these enzymes are a component of restriction-modification systems and serve as valuable tools for the manipulation of DNA. The structure of HhaI methyltransferase (M.HhaI) has been resolved to 2.5 A: the molecule folds into 2 domains - a larger catalytic domain containing catalytic and cofactor binding sites, and a smaller DNA recognition domain.
De novo and maintenance DNA MTases
De novo methyltransferases recognize something in the DNA that allows them to newly methylate cytosines. These are expressed mainly in early embryo development and they set up the pattern of methylation.
Maintenance methyltransferases add methylation to DNA when one strand is already methylated. These work throughout the life of the organism to maintain the methylation pattern that had been established by the de novo methyltransferases IS.
Mammalian DNA methyltransferase (DNMT)
DNMT3L is a protein closely related to DNMT3A and DNMT3B in structure and critical for DNA methylation, but appears to be inactive on its own.
DNMT1 is the most abundant DNA methyltransferase in mammalian cells, and considered to be the key maintenance methyltransferase in mammals. It predominantly methylates hemimethylated CpG di-nucleotides in the mammalian genome. This enzyme is 7– to 100-fold more active on hemimethylated DNA as compared with unmethylated substrate in vitro, but it is still more active at de novo methylation than other DNMTs. The recognition motif for the human enzyme involves only three of the bases in the CpG dinuclotide pair: a C on one strand and CpG on the other. This relaxed substrate specificity requirement allows it to methylate unusual structures like DNA slippage intermediates at de novo rates that equal its maintenance rate. Like other DNA cytosine-5 methyltransferases the human enzyme recognizes flipped out cytosines in double stranded DNA and operates by the nucleophilic attack mechanism. In human cancer cells DNMT1 is responsible for both de novo and maintenance methylation of tumor suppressor genes. The enzyme is about 1,620 amino acids long. The first 1,100 amino acids constitute the regulatory domain of the enzyme, and the remaining residues constitute the catalytic domain. These are joined by Gly-Lys repeats. Both domains are required for the catalytic function of DNMT1.
DNMT1 has several isoforms, the somatic DNMT1, a splice variant (DNMT1b) and an oocyte-specific isoform (DNMT1o). DNMT1o is synthesized and stored in the cytoplasm of the oocyte and translocated to the cell nucleus during early embryonic development, while the somatic DNMT1 is always found in the nucleus of somatic tissue.
DNMT1 null mutant embryonic stem cells were viable and contained a small percentage of methylated DNA and methyltransferase activity. Mouse embryos homozygous for a deletion in Dnmt1 die at 10–11 days gestation.
TRDMT1 (formerly known as DNMT2)
Although this enzyme has strong sequence similarities with 5-methylcytosine methyltransferases of both prokaryotes and eukaryotes, in 2006, the enzyme was shown to methylate position 38 in aspartic acid transfer RNA and does not methylate DNA. To reflect this different function, the name for this methyltransferase has been changed to TRDMT1 (tRNA aspartic acid methyltransferase 1) to better reflect its biological function. TRDMT1 is the first RNA cytosine methyltransferase to be identified in a human.
DNMT3 is a family of DNA methyltransferases that could methylate hemimethylated and unmethylated CpG at the same rate. The architecture of DNMT3 enzymes is similar to that of DNMT1, with a regulatory region attached to a catalytic domain. There are three known members of the DNMT3 family: DNMT3a, 3b, and 3L.
DNMT3a and DNMT3b can mediate methylation-independent gene repression. DNMT3a can co-localize with heterochromatin protein (HP1) and methyl-CpG-binding protein (MeCBP). They can also interact with DNMT1, which might be a co-operative event during DNA methylation. DNMT3a prefers CpG methylation to CpA, CpT, and CpC methylation, though there appears to be some sequence preference of methylation for DNMT3a and DNMT3b. DNMT3a methylates CpG sites at a rate much slower than DNMT1, but greater than DNMT3b.
DNMT3L contains DNA methyltransferase motifs and is required for establishing maternal genomic imprints, despite being catalytically inactive. DNMT3L is expressed during gametogenesis when genomic imprinting takes place. The loss of DNMT3L leads to bi-allelic expression of genes normally not expressed by the maternal allele. DNMT3L interacts with DNMT3a and DNMT3b and co-localized in the nucleus. Though DNMT3L appears incapable of methylation, it may participate in transcriptional repression.
- Vidaza (5-azacitidine) in a phase II trial for AML
- Dacogen (decitabine) in phase III trials for AML and CML
- ^ Loenen WA, Daniel AS, Braymer HD, Murray NE (November 1987). "Organization and sequence of the hsd genes of Escherichia coli K-12". J. Mol. Biol. 198 (2): 159–70. doi:10.1016/0022-2836(87)90303-2. PMID 3323532.
- ^ Narva KE, Van Etten JL, Slatko BE, Benner JS (December 1988). "The amino acid sequence of the eukaryotic DNA [N6-adenine]methyltransferase, M.CviBIII, has regions of similarity with the prokaryotic isoschizomer M.TaqI and other DNA [N6-adenine] methyltransferases". Gene 74 (1): 253–9. doi:10.1016/0378-1119(88)90298-3. PMID 3248728.
- ^ Lauster R (March 1989). "Evolution of type II DNA methyltransferases. A gene duplication model". J. Mol. Biol. 206 (2): 313–21. doi:10.1016/0022-2836(89)90481-6. PMID 2541254.
- ^ a b c Timinskas A, Butkus V, Janulaitis A (May 1995). "Sequence motifs characteristic for DNA [cytosine-N4] and DNA [adenine-N6] methyltransferases. Classification of all DNA methyltransferases". Gene 157 (1–2): 3–11. doi:10.1016/0378-1119(94)00783-O. PMID 7607512.
- ^ Labahn J, Granzin J, Schluckebier G, Robinson DP, Jack WE, Schildkraut I, Saenger W (November 1994). "Three-dimensional structure of the adenine-specific DNA methyltransferase M.Taq I in complex with the cofactor S-adenosylmethionine". Proc. Natl. Acad. Sci. U.S.A. 91 (23): 10957–61. doi:10.1073/pnas.91.23.10957. PMC 45145. PMID 7971991. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=45145.
- ^ Kelleher, J. E.; Daniel, A. S.; Murray, N. E. (1991). "Mutations that confer de novo activity upon a maintenance methyltransferase". Journal of molecular biology 221 (2): 431–440. doi:10.1016/0022-2836(91)80064-2. PMID 1833555.
- ^ Posfai J, Bhagwat AS, Roberts RJ (December 1988). "Sequence motifs specific for cytosine methyltransferases". Gene 74 (1): 261–5. doi:10.1016/0378-1119(88)90299-5. PMID 3248729.
- ^ a b Kumar S, Cheng X, Klimasauskas S, Mi S, Posfai J, Roberts RJ, Wilson GG (January 1994). "The DNA (cytosine-5) methyltransferases". Nucleic Acids Res. 22 (1): 1–10. doi:10.1093/nar/22.1.1. PMC 307737. PMID 8127644. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=307737.
- ^ Lauster R, Trautner TA, Noyer-Weidner M (March 1989). "Cytosine-specific type II DNA methyltransferases. A conserved enzyme core with variable target-recognizing domains". J. Mol. Biol. 206 (2): 305–12. doi:10.1016/0022-2836(89)90480-4. PMID 2716049.
- ^ Cheng X (February 1995). "DNA modification by methyltransferases". Curr. Opin. Struct. Biol. 5 (1): 4–10. doi:10.1016/0959-440X(95)80003-J. PMID 7773746.
- ^ Cheng X, Kumar S, Posfai J, Pflugrath JW, Roberts RJ (July 1993). "Crystal structure of the HhaI DNA methyltransferase complexed with S-adenosyl-L-methionine". Cell 74 (2): 299–307. doi:10.1016/0092-8674(93)90421-L. PMID 8343957.
- ^ Mark R. Kho, David J.Baker, Ali Layoon, and Steven S. Smith (1998). "Stalling of Human DNA (Cytosine-5) Methyltransferase at Single Strand Conformers form a Site of Dynamic Mutation". Journal of Molecular Biology 275 (1): 67–79. doi:10.1006/jmbi.1997.1430. PMID 9451440.
- ^ Steven S. Smith, Bruce E. Kaplan, Lawrence C. Sowers and Edward M. Newman (1992). "Mechanism of human methyl-directed DNA methyltransferase and the fidelity of cytosine methylation". Proceedings of the National Academy of Science, U.S.A. 89 (10): 4748–4744. PMC 49160. PMID 1584813. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=49160.
- ^ Kam-Wing Jair, Kurtis E. Bachman, Hiromu Suzuki, Angela H.Ting, Ina Rhee, Ray-Whay Chiu Yen, Stephen B. Baylin and Kornel E. Schuebel (2006). "De novo CpG Island Methylation in Human Cancer Cells". Cancer Research 69 (2): 682–692. doi:10.1158/0008-5472.CAN-05-1980. PMID 16423997.
- ^ Angela H. Ting, Kam-wing Jair, Kornel E. Schuebel and Stephen B. Baylin (2006). "Differential Requirement for DNA Methyltransferse 1 In Maintianing Cancer Cell Gene Promoter Hypermethylation". Cancer Research 66 (2): 729–735. doi:10.1158/0008-5472.CAN-05-1537. PMID 16424002.
- ^ En Li, Timothy H. Bestor, and Rudolf Jaenisch (1992). "Targeted Mutation of the DNA Methyltransferase Gene Results in Embryonic Lethality". Cell 69 (6): 915–926. doi:10.1016/0092-8674(92)90611-F. PMID 1606615.
- ^ M.G. Goll, F. Kirpekar, K.A. Maggert, J.A. Yoder, C-L. Hsieh, X. Zhang, K.G. Golic, S.E. Jacobsen, T.H. Bestor (2006). "Methylation of tRNAAsp by the DNA Methyltransferase Homolog Dnmt2". Science 311 (5759): 395–398. doi:10.1126/science.1120976. PMID 16424344. http://www.sciencemag.org/cgi/content/abstract/311/5759/395.
- ^ "TRDMT1 tRNA aspartic acid methyltransferase 1 (Homo sapiens)". Entrez Gene. NCBI. 2010-11-01. http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1787. Retrieved 2010-11-07.
- ^ http://www.nature.com/nbt/journal/v28/n12/fig_tab/nbt.1724_T3.html
- ^ http://www.nature.com/nbt/journal/v28/n12/full/nbt.1724.html
- S S Smith (1994). Biological Implications of the Mechanism of Action of Human DNA (Cytosine-5) Methyltransferase Progress in Nucleic Acids Research and Molecular Biology 49: 65–111. 
- S Pradhan & PO Esteve (2003). Mammalian DNA (cytosine-5) methyltransferases and their expression. Clinical Immunology 109: 6–16. 
- MG Goll and TH Bestor (2005). Eukaryotic cytosine methyltransferase. Annual Review of Biochemistry 74: 481–514 
- Svedruzić ZM (2008). "Mammalian cytosine DNA methyltransferase Dnmt1: enzymatic mechanism, novel mechanism-based inhibitors, and RNA-directed DNA methylation". Curr. Med. Chem. 15 (1): 92–106. doi:10.2174/092986708783330700. PMID 18220765.
- Information about DNA methyltransferases and DNA methylation at epigeneticstation.com
- Data for a DNA methyltransferase (DNMT) Antibody
- MeSH DNA+Modification+Methyltransferases
Transferase: one carbon transferases (EC 2.1) 2.1.1: Methyl-N-O-Other 2.1.2: Hydroxymethyl-,
Formyl- and RelatedHydroxymethyltransferaseFormyltransferaseOther
2.1.3: Carboxy- and CarbamoylCarboxyCarbamoyl 2.1.4: AmidinoArginine:glycine amidinotransferase Transcriptional regulationprokaryoticeukaryoticboth Promotion Initiation (prokaryotic,
eukaryotic)Transcription start site
Wikimedia Foundation. 2010.
Look at other dictionaries:
DNA methyltransferase — n a methyltransferase that promotes the covalent addition of a methyl group to a specific nucleotide base in a molecule of DNA * * * DNA meth·yl·trans·fer·ase (meth″əl transґfər ās) any of a group of enzymes that catalyze the … Medical dictionary
DNA-Methyltransferase — DNA Methyltransferasen Enzymklassifikation EC, Kategorie … Deutsch Wikipedia
O-6-methylguanine-DNA methyltransferase — PDB rendering based on 1eh6 … Wikipedia
O6-Methylguanin-DNA-Methyltransferase — Bänder /Oberflächenmodell von MGMT auf O6 Methylguanyl DNA na … Deutsch Wikipedia
6-O-Methylguanin-DNA-Methyltransferase — O6 Methylguanin DNA Methyltransferase Bänder /Oberflächenmodell von MGMT auf O6 Methylguanyl DNA nach PDB … Deutsch Wikipedia
DNA methylase — DNA meth·yl·ase (methґəl ās) DNA methyltransferase … Medical dictionary
DNA methylation — Illustration of a DNA molecule that is methylated at the two center cytosines. DNA methylation plays an important role for epigenetic gene regulation in development and disease. DNA methylation is a biochemical process that is important for… … Wikipedia
Methyltransferase — HaeIII methyltransferase / DNA. Rendered from PDB 1DCT … Wikipedia
DNA-Methylierung — Übergeordnet epigenetische Regulation der Genexpression Methylierung von Makromolekülen DNA Modifikation … Deutsch Wikipedia
methyltransferase — Any enzyme transferring methyl groups from one compound to another. SYN: demethylase, methylkinase, transmethylase. * * * meth·yl·trans·fer·ase tran(t)s fər .ās, .āz n any of several transferases that promote transfer of a methyl group from one… … Medical dictionary