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)

Nicotinamide was found to be a potent inhibitor of DNA methylation in vivo without interfering with protein or DNA synthesis. The inhibition of DNA methylation in a phage-infected cell resulted in a parallel decrease in the production of viable virus particles. In vitro experiments revealed that nicotinamide inhibits DNA methylase activity in a competitive fashion with respect to S-adenosylmethionine and non-competitively with respect to DNA. These results were interpreted to mean that DNA methylation is an essential step in the process of maturation of the bacteriophage phichi174.
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PMID:Studies on the biological role of DNA methylation: inhibition of methylation and maturation of the bacteriophage phichi174 by nicotinamide. 12 65

DNA methylase has been purified 405-fold from Krebs II ascites cells. The purified enzyme is homogeneous on SDS-poly acrylamide gel electrophoresis (molecular weight about 80,000) and the only product of the reaction with DNA is 5-methyl cytosine. Both native and denatured DNA are methylated by the enzyme; with calf thymus DNA the double stranded form is the better substrate but the enzyme preferentially methylates single stranded E.coli DNA even in "native" preparations. Our results do not support a mechanism whereby the enzyme methylates DNA by binding irreversibly and "walking" along it. By measuring maximum levels of methylation of DNAs from different sources we have estimated the proportion of unmethylated sites present in them. Homologous ascites DNA can be methylated, but only to about 5% of the level of the best substrate, undermethylated mouse L929 cell DNA. DNA isolated from growing cells or tissues is a better substrate than DNA from normal liver or pancreas, or from stationary cells.
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PMID:DNA methylase: purification from ascites cells and the effect of various DNA substrates on its activity. 13 36

Partial purification of DNA methylase from Novikoff rat hepatoma cells is described. Contamination with other proteins persists although the enzyme preparation has a high specific activity and is purified 980-fold over homogenate activity. Evidence suggests, but does not prove, that there may be more than one species of DNA methylase in these cells. The enzyme has two broad pH optima at pH 7.0 and 7.5 and most readily methylates heterologous denatured DNAs although complex reaction kinetics indicate that native DNAs may eventually be methylated to an equal or greater level. The preparation of undermethylated DNA from Novikoff cells is also described. Undermethylated homologous DNA is an 85-fold greater acceptor of methyl groups than fully methylated Novikoff cell DNA. In contrast to other DNA substrates, the enzyme preparation methylates native undermethylated homologous DNA at a 3.5-fold greater than denatured undermethylated homologous DNA.
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PMID:S-adenosylmethionine: DNA-cytosine 5-methyltransferase from a Novikoff rat hepatoma cell line. 17 25

The existence of a DNA-dependent protein methylase activity without any concomitant DNA methylase activity was demonstrated in bull seminal plasma. The enzyme utilized S-adenosyl-L-methionine as a methyl donor, and endogenous seminal plasma protein as the substrate. There was no demonstrable enzyme activity when the seminal plasma was preheated at 100 degrees for 10 min, or when the enzyme reaction mixture was incubated at 4 degrees. The protein methylase required a heterologous DNA source, had optimal activity at pH 8.1, and was enhanced in the presence of Mg2+, NH4+, and reduced glutathione. After the methylated protein product was separated from DNA by extraction with 0.2 M HCl, the incorporated radioactivity was shown to be totally solubilized by incubating the protein either with Pronase or 1 M NaOH, while RNase and DNase had no effect. Approximately 70% of the enzymatically synthesized amino acids in the protein product were tentatively identified as O-methylated amino acid ethers by virtue of their elution from a Dowex 50 H+ column with 0.2 M pyridine, and their stability to acid and base hydrolysis. The partially purified methylated product was shown by Sephadex G-50 chromatography to consist of three distinct radioactive proteins with molecular weights of approximately 21,000, 15,000, and 10,000.
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PMID:DNA-dependent protein methylase activity in bull seminal plasma. 24 Mar 99

Base composition, content of pyrimidine isopliths and the degree of methylation of mitochondrial DNA (mtDNA) and nuclear DNA (nDNA) from various vertebrates and protozoon Crithidia oncopelti have been studied. MtDNAs from mammals (ox, rat) do not differ in fact in the GC content from the respective nDNA. The GC content in mtDNA from fishes (sheat fish) and birds (duck, chicken) is 1.5-2.5 mole % higher than in the respective nDNA. Kinetoplast DNA (kDNA) from Crithidia oncopelti (GC = 42.9 mole %) differs significantly in base composition from nDNA (GC = 51.3 mole %). All the mtDNA and kDNA studied differ from the respective nDNA by a lower degree of pyrimidine clustering. The amount of mono and dipyrimidine fragments in mtDNA is more than 30 mole %, whereas in nDNA it does not exceed 23 mole %. The quantity of long pyrimidine clusters (hexa and others) is 2-4 times lower in mtDNA than in nDNA. The lower degree of clustering of pyrimidine nucleotides seems to be a specific feature of all the mtDNA studied. This may be indicative of common traits in the organization and origin of mtDNA. All mtDNA of vertebrates contain 5-methylcytosine as a 'minor' base (1.5- 3.15 mole %) and surpass by 1.5-2 times the respective nDNA in the methylation degree. It has been found that in animals mtDNA is species specific as far as the 5-methyl-cytosine content is concerned. In mitochondria and nuclei of rat liver certain DNA methylase activity has been detected, which provides in vitro the methylation of cytosine residues both in homologous DNA and various heterologous DNAs. The specificity of methylation in vitro of cytosine residues in the same heterologous DNA from E. coli B varies with the source of enzymes. The mitochondrial enzyme methylates cytosine as the lone monopyrimidine residue, whereas the nuclear enzyme methylase cytosine in the di- and tripyrimidine fragments.
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PMID:The structure of animal mitochondrial DNA (base composition, pyrimidine clusters, character of methylation). 32 87

The sequence specificity of an extensively purified DNA methylase preparation from Krebs II mouse ascites cells has been examined. The enzyme appears to be highly sequence dependent. Moreover the sequence distribution of cytosine residues that are methylated, bears a very close resemblance to the sequence distribution of 5'-methyl cytosine found in vivo in a wide range of vertebrate cells and is consistent with methylation of cytosines in the sequence R-Yn-C-R.
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PMID:The sequence specificity of a mammalian DNA methylase. 32 23

Site-specific genetic recombinations promoted in vivo by the EcoRI endonuclease has been demonstrated by using constructed hybrid plasmids in which the chloramphenicol resistance gene was inactivated by insertion of DNA fragments at an EcoRI site within the gene. Such recombination can involve either the joining of intracellularly generated cohesive termini of the same DNA fragment or intermolecular ligation of different DNA fragments. DNA cleavage and ligation in vivo are precise: recombinant DNA molecules show functional continuity of the gene sequence cleaved by the enzyme and regeneration of nucleotide recognition sites for both the EcoRI endonuclease and the EcoRI DNA methylase. In other experiments, EcoRI-generated fragments of eukaryotic DNA that had not been modified by the Escherichia coli K methylase were shown to be taken up by bacterial cells and to undergo intracellular ligation to segments of bacterial plasmid DNA.
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PMID:In vivo site-specific genetic recombination promoted by the EcoRI restriction endonuclease. 33 2

An endonuclease having EcoRI specificity is produced by bacteria containing the ColE1 plasmid. Such bacterial cells fail to express restriction or modification functions in vivo, and phage or plasmid DNA obtained from ColE1-containing cells has unmodified EcoRI sites that are cleaved in vitro by purified EcoRI endonuclease or by enzyme extracted from bacteria that carry ColE1. No EcoRI DNA methylase activity associated with ColE1 has been detected. The finding of phenotypically cryptic ColE1-dependent EcoRI endonuclease activity and the absence of any detectable EcoRI modification system in ColE1-containing cells suggest a control mechanism that appears to prevent functional expression of the ColE1-determined enzyme in vivo.
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PMID:Phenotypically cryptic EcoRI endonuclease activity specified by the ColE1 plasmid. 34 63

It was shown that E. coli C, E. coli MRE 600 DNA, and also plasmid DNA of Col E1, RSF 2124 from E. coli K-12, and plasmid DNA from E. coli MRE 600 were completely resistant against restriction endonuclease R. Eco RII. Plasmid DNAs of Col E1, RSF 2124 amplificated for 4 hours in the presence of chloramphenicol are sensitive to R. Eco RII but after 16-hour amplification in the presence of chloramphenicol these DNAs acquire complete resistance against R. Eco RII. These data point to the slower rate of modification of DNA in vivo by DC-methylases of Eco RII type in comparison with DNA methylase Eco RII.
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PMID:[Sensitivity of chromosomal and plasmid E. coli DNA to restriction endonuclease Eco RII]. 36 77

DNA methylase methylating adenine with formation of 6-methylaminopurine has been identified in Shigella sonnei 1188 cells which are the natural host of DDVI phage. At the same time, in DNA of DDVI phage replicating both in Sh. sonnei 1188 cells and in Escherichia coli B cells 7-methylguanine was found as the only minor base in amounts of 0.25 and 0.27 mol per 100 mol of nucleotides, respectively. The extract of the infected cells was found to contain both kinds of DNA methylases: virus-specific guanine methylase and cellular adenine methylase. The lack of 6-methylaminopurine in DNA of this phage is explained by reversible inhibition of the cell enzyme in the infected cells. The amount of methyl groups transferred by DDVI-specific methylase on DNA does not depend on the species of the infected cells and is similar in the case of unmodified SD phage DNA and DNA of T2 phage methylated by E. coli B enzyme. Guanine methylase has been shown to be a DDVI-induced modification enzyme and to protect against restriction of B-type. It methylates double-stranded DNAs only and is inhibited by S-adenosylhomocysteine.
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PMID:Specificity and functions of guanine methylase of Shigella sonnei DDVI phage. 36 9


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