Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.1.1.37 (DNA methyltransferase)
4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA methyltransferase activity has been observed in a total crude homogenate of rice cells grown in suspension culture using either native plant DNA or, under the conditions used, the more responsive hemimethylated poly (dI-MedC).poly(dI-dC). Using the latter substrate we have purified an enzyme fraction 380-fold by salt extraction of chromatin, DEAE cellulose and phosphocellulose. This purified fraction showed enzyme activity only with poly (dI-MedC).poly(dI-dC) thus suggesting the occurrence in plants of a DNA methyltransferase specific for hemimethylated DNA. A Mr value of 54000 was calculated on the basis of the sedimentation coefficient which was determined by sucrose density gradient centrifugation. Apparent Km values for poly (dI-MedC).poly(dI-dC) and S-adenosyl-L-methionine were found to be 17 micrograms/ml and 2.6 microM, respectively.
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PMID:Purification and properties of a novel DNA methyltransferase from cultured rice cells. 204 93

Procainamide, a widely used antiarrythmic, causes DNA hypomethylation in the human T cell line Jurkat, but the mechanism is unknown. We report that procainamide inhibits the DNA methyltransferase catalyzed transfer of methyl groups from S-adenosylmethionine to DNA, but has no effect on other known regulators of DNA methylation. Our results suggest that procainamide could inhibit cellular DNA methylation by inhibiting DNA methyltransferase activity.
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PMID:Procainamide inhibits DNA methyltransferase in a human T cell line. 206 44

The qualitative and quantitative features of mutagenesis by two DNA adducts of carcinogenic alkylating agents, O6-methylguanine (m6G) and O4-methylthymine (m4T), were examined in vivo. The deoxyhexanucleotides 5'-GCTAGC-3' and 5'-GCTAGC-3' were synthesized, where the underlined bases are the positions of m4T or m6G, respectively. By use of recombinant DNA techniques, the respective hexanucleotides or an unmodified control were inserted into a six-base gap in the otherwise duplex genome of the Escherichia coli virus M13mp19-NheI. The duplex adducted genome was converted to single-stranded form and introduced into an E. coli strain that was phenotypically normal with regard to m6G/m4T repair, a strain deficient in repair by virtue of an insertion in the gene encoding the Ada-m6G/m4T DNA methyltransferase, or the same two cell lines after challenge with N-methyl-N'-nitro-N-nitrosoguanidine. Treatment with this alkylating agent chemically compromises alkyl-DNA repair functions. The mutation efficiency of m6G was low or undetectable (0-1.7%) in all cell systems tested, owing, we believe, to rapid repair. In striking contrast, the mutagenicity of m4T was high (12%) in cells fully competent to repair alkylation damage and was roughly doubled when those cells were pretreated with N-methyl-N'-nitro-N-nitrosoguanidine to suppress repair. Taken together, these data suggest that m4T is potentially more mutagenic than m6G and, if formed by a DNA methylating agent, may pose a significant threat to the genetic integrity of an organism.
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PMID:Comparative mutagenesis of O6-methylguanine and O4-methylthymine in Escherichia coli. 206 60

The Bacillus subtilis FI DNA methyltransferase (M.BsuFI) modifies the outer cytosine of the DNA sequence CCGG, causing resistance against R.BsuFI and R.MspI restriction. The M.BsuFI gene was cloned and expressed in B.subtilis and Escherichia coli. As derived from the nucleotide sequence, the M.BsuFI protein has 409 amino acids, corresponding to a molecular mass of 46,918 daltons. Including these data we have compared the nucleotide and amino acid sequences of different CCGG recognizing enzymes. These analyses showed that M.BsuFI is highly related to two other CCGG specific methyltransferases, M.MspI and M.HpaII, which were isolated from Gram-negative bacteria. Between M.BsuFI and M.MspI the sequence similarity is particularly significant in a region, which has been postulated to contain the target recognition domains (TRDs) of cytosine-specific DNA methyltransferases. Apparently M.BsuFI and M.MspI, derived from phylogenetic distant organisms, use highly conserved structural elements for the recognition of the CCGG target sequence. In contrast the very same region of M.HpaII is quite different from those of M.BsuFI and M.MspI. We attribute this difference to the different targeting of methylation within the sequence CCGG, where M.HpaII methylates the inner, M.BsuFI/M.MspI the outer cytosine. Also the CCGG recognizing TRD of the multispecific B.subtilis phage SPR Mtase is distinct from that of the host enzyme, possibly indicating different requirements for TRDs operative in mono- and multispecific enzymes.
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PMID:The amino acid sequence of the CCGG recognizing DNA methyltransferase M.BsuFI: implications for the analysis of sequence recognition by cytosine DNA methyltransferases. 210 58

The Chlorella virus IL-3A gene encoding the DNA methyltransferase M.CviJI, which methylates the internal cytosine in (G/A)GC(T/C/G) sequences, was cloned and expressed in Escherichia coli. The region containing the M.CviJI gene was sequenced and a single open reading frame of 1101 bp was identified that could code for a polypeptide of 367 amino acids with a predicted molecular weight of 41,864. M.CviJI contained regions of amino acids which were similar to bacterial cytosine methyltransferases. Eighteen other Chlorella viruses, of 36 tested, contained DNA sequences which hybridized to the M.CviJI gene; DNA from some, but not all, of these 18 viruses also contained 5-methylcytosine in (G/A)GC(T/C/G) sequences.
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PMID:Cloning and sequencing the cytosine methyltransferase gene M. CviJI from Chlorella virus IL-3A. 215 87

EcoRI DNA methyltransferase (MTase) is rapidly inactivated by N-ethylmaleimide with concomitant incorporation of 2 mol of N-ethyl[2-3H]maleimide/mol of functional monomer. Preincubation of the enzyme with either S-adenosylmethionine or DNA reduces the rate of activity loss, whereas preincubation with DNA and the S-adenosylmethionine analog sinefungin completely protects the enzyme from inactivation. An endo proteinase Glu-C digest of N-ethyl[2-3H]maleimide-modified enzyme was prepared and separated by high pressure liquid chromatography. Modified and unmodified cysteine-containing peptides were located and identified by radioactivity, mass spectrometry, and tandem mass spectrometry. In the absence of any ligands, cysteines 25, 116, and 223 are modified by N-ethylmaleimide; in the presence of DNA and sinefungin, Cys-223 is essentially unmodified. Thus, N-ethylmaleimide modification of Cys-223 in EcoRI DNA MTase is responsible for the loss of enzyme activity. Cys-223 is preceded by Asn, and this (or Cys-Asn) occurs with high frequency in adenine and cytosine (N-4) DNA MTases. Direct involvement of cysteine in methyl transfer reactions to adenine N-6 and cytosine N-4 is supported by the similarity of the reactions catalyzed by adenine N-6 and cytosine N-4 DNA MTases, the frequent presence of Asn-flanking Cys, and the importance of Cys-223 to EcoRI MTase function.
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PMID:Identification of a critical cysteine in EcoRI DNA methyltransferase by mass spectrometry. 217 Mar 93

The gene coding for the GGTNACC specific Ecal DNA methyltransferase (M.Ecal) has been cloned in E. coli from Enterobacter cloacae and its nucleotide sequence has been determined. The ecalM gene codes for a protein of 452 amino acids (Mr: 51,111). It was determined that M.Ecal is an adenine methyltransferase. M.Ecal shows limited amino acid sequence similarity to other adenine methyltransferases. A clone that expresses Ecal methyltransferase at high level was constructed.
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PMID:Cloning and nucleotide sequence of the gene encoding the Ecal DNA methyltransferase. 218 82

O6-Methylguanine-DNA methyltransferase (MT) specific activity (fmol/mg protein) was measured in human T lymphocytes which were maintained as exponentially growing cultures from 6 to 17 days. The T lymphocytes were not transformed and were grown under the same conditions used previously for determination of spontaneous human mutant frequencies. Although large inter-individual differences in activity were found, the differences were not attributable to donor age, sex or time in culture. The reported specific activity results, including the age and sex independence, were similar to other laboratories even though non-cultured peripheral blood T lymphocytes were previously used. Since cells from Alzheimer's disease (AD) patients have been shown to be overly sensitive to alkylation damage induced by N-methyl-N'-nitro-N-nitrosoguanine, and since no one has previously assayed MT activity in cells from AD patients, we compared MT activities in cultured T lymphocytes from AD patients, healthy controls and neurological controls. Similar levels of MT specific activity were found in each category analysed.
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PMID:O6-methylguanine-DNA methyltransferase activities from exponentially growing human T lymphocytes: similar activities in controls and Alzheimer's disease patients. 218 70

We have identified a DNA methyltransferase activity of the nitrogen-fixing bacterium, Rhizobium meliloti, that repairs O6-methylguanine lesions. Repair of the O6-methylguanine residue results in transfer of the methyl group to a cysteine residue of a 28,000-dalton protein. The O6-methyltransferase activity is expressed constitutively and R. meliloti does not exhibit an adaptive response to alkylating agents.
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PMID:A constitutive O6-methylguanine-DNA methyltransferase of Rhizobium meliloti. 218 20

O6-Methylguanine-DNA methyltransferase, present in most organisms, removes mutagenic and carcinogenic O6-alkylguanine from DNA by accepting the alkyl group in a stoichiometric reaction. The protein has been partially purified from human placenta. It reacts with second-order rate constants of 2.20 x 10(8) and 0.067 x 10(8) lmol-1 min-1 at 37 degrees C for duplex and single-stranded DNA substrates, respectively. The corresponding value for the alkylated base in synthetic poly(dC, dG, m6dG) is 0.02 x 10(8) l mol-1 min-1. The native protein is monomeric with a molecular mass of 22-24 kDa. Methylation of the protein does not lead to a gross change in its conformation but causes a slight reduction in its isoelectric point of 6.2. Although DNA protects the protein from heat inactivation, both duplex and single-stranded DNAs inhibit its activity in a concentration-dependent manner. The transferase reaction rate is also strongly inhibited by salt with about 20% of the maximum rate observed in physiological ionic strength. This inhibition is nonspecific with respect to the ions of univalent salts.
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PMID:Physicochemical studies of human O6-methylguanine-DNA methyltransferase. 222 57


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