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)

Deoxyribonucleic acid (DNA)-cytosine methylation specified by the wild-type Escherichia coli K 12 mec+ gene and by the N-3 drug resistance (R) factor was studied in vivo and in vitro. Phage lambda and fd were propagated in the presence of L-[methyl-3H]methionine in various host bacteria. The in vivo labeled DNA was isolated from purified phage and depurinated by formic acid-diphenylamine treatment. The resulting pyrimidine oligonucleotide tracts were separated according to size and base composition by chromatography on diethylaminoethyl-cellulose in 7 M urea at pH 5.5 and 3.5, respectively. The distribution of labeled 5-methylcytosine in DNA pyrimidine tracts was identical for phage grown in mec+ and mec minus (N-3) cells. For phage lambda the major 5-methylcytosine containing tract was the tripyrimidine, C2T; for both fd-mec minus (N-3) DNA and fd-mec+DNA, C2T was the sole 5-methylcytosine-containing tract. When various lambda DNAs were methylated to saturation in vitro by crude extracts from mec+ and mec minus (N-3) cells, the extent of cytosine methylation was the same. This is in contrast to in vivo methylation where lambda-mec minus (N-3) DNA contains twice as many 5-methylcytosines per genome as lambda-mec+ DNA. Therefore, we suggest that the K12 met+ cytosine methylase and the N-3 plasmid modification methylase are capable of recognizing the same nucleotide sequences, but that the in vivo methylation rate is lower in mec+ cells.
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PMID:Deoxyribonucleic acid-cytosine methylation by host- and plasmid-controlled enzymes. 109 19

(Deoxyribonucleic acid from Micrococcus luteus was methylated in vitro in the presence of S-adenosyl-(14C methyl)methionine with a DNA methyltransferase purified from extracts of te. coli infected with bacteriophage T2. The labelled DNA was degraded by enzymatic and specific chemical methods and the resulting short oligonucleotides were separated and characterized. tthe analytical data permit the conclusion that the tdna transmethylase reacts specifically with N-G-A-T-C-N sequences in which it converts adenine to a 6-methyl-aminopurine residue.
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PMID:Specificity of deoxyribonucleic acid transmethylase induced by bacteriophage T2. I. Nucleotide sequences isolated from tmicrococcus luteus DNA methylated in vitro. 110 Dec 23

On growing the cells of Bacillus brevis S methionine-auxotroph mutant in the presence of [Me-3H]methionine, practically all the radioactivity incorporated into DNA is found to exist in 5-methylcytosine and N6-methyladenine. The analysis of pyrimidine isopliths isolated from DNA shows that radioactivity only exists in mono- and dinucleotides and the content of 5-methylcytosine in R-m5 C-R and R-m5 C-T-R oligonucleotides is equal. The analysis of dinucleotides isolated from DNA by means of pancreatic DNAase hydrolysis allows the nature of purine residues neighbouring 5-methylcytosine to be identified and shows that 5-methylcytosine localizes in G-m5 C-A and G-m5 C-Tr fragments. B. brevis S DNA methylase modifying cytosine residues recognizes the GCA/TGC degenerate nucleotide sequence which is a part of the following complementary structure with a two-fold rotational axis of symmetry: (5')...N'-G-C-T-G-C-N... (3') (3')...N-C-G-A-C-G-N'... (5') (Methylated cytosine residues are askerisked). Cytosine-modifying DNA methylase activity is isolated from B. brevis cells; it is capable of methylating in vitro homologous and heterologous DNA. Hence DNA in bacterial cells can be undermethylated. This enzyme methylates cytosine residues in native and denatured DNA in the same nucleotide sequences. Specificity of methylation of cytosine residues in vitro and in vivo does not depend on the nature of substrate DNA. DNA methylases of different variants of B. brevis (R, S, P+, P-)) methylate cytosine residues in the same nucleotide sequences. It means that specificity or methylation of DNA cytosine residues in the cells of different variants of B. brevis is the same.
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PMID:On the nature of the cytosine-methylated sequence in DNA of Bacillus brevis var. G.-B. 118 Sep 70

A DNA methylase has been purified 270-fold from HeLa cell nuclei by chromatography on DEAE-cellulose, phosphocellulose, and hydroxyapatite. The enzyme transfers methyl groups from S-adenosyl-L-methionine to cytosine residues in DNA. The sole product of the reaction has been identified as 5-methylcytosine. The enzyme is able to methylate homologous (HeLa) DNA, although to a lesser extent than heterologous DNA. This may be due to incomplete methylation of HeLa DNA synthesized in vivo. The HeLa enzyme can methylate single-stranded DNA, and does so to an extent three times greater than that of the corresponding double-stranded DNA. In single-stranded M. luteus DNA, at least 2.4% of the cytosine residues can be methylated in vitro by the enzyme. The enzyme also can methylate poly (dG-dC-dG-dC) and poly (dG, dC). Bilateral nearest neighbors to the 5-methylcytosine have been determined with M. luteus DNA in vitro and HeLa DNA in vivo. The 5' neighbor can be either G or C while the 3' neighbor is always G and this sequence is, thus, p(G/C)pmCpG.
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PMID:DNA methylase from HeLa cell nuclei. 118 40

After intravenous hydrocortisone injection (2 mg per 100 g of animal weight) DNA methylase activity in rat liver increases 1.5-2 times. Rat liver DNA is capable of being methylated in vitro by homologous and heterologous (from rat spleen and ascite carcinoma cells) enzymes. Rat liver DNA isolated 40 min after hydrocortisone injection contains 1.5 times more 5-methylcytosine and is able to accept 1.5 times less methyl groups from (3H-methyl)-S-adenosylmethionine in the in vitro methylation reaction by enzymes from rat spleen as compared to liver DNA isolated from nontreated rats. Thus, there is DNA supermethylation in rat liver cells occurring under the action of the hormone. This induced change in the methylation level of DNA in rat liver is reversible: 6 hours after a single hydrocortisone injection the amount of 5-methylcytosine in DNA decreases to normal, and the DNA ability to accept methyl groups in the in vitro methylation is the same as compared to that of liver DNA from control animals. The induced reversible DNA methylation is to be considered as a mechanism for the regulation of DNA transcription and cell genetic activity.
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PMID:[Rat liver methylation of nuclear DNA following hydrocortisone induction]. 127 66

The alpha-fetoprotein gene is conceived as being methylated in the zygote and according to the model is in a heterochromatic state and is therefore in a non-functional condition. Specific DNA methylase genes would produce methylases capable of alkylating enhancer regions of alpha-fetoprotein and certain proteins that would alter the heterochromatin condition. Also involved is a gene for the synthesis of a conformational-inducer protein that is proposed to be capable of blocking genic regions from reheterochromatizing. One of the pivotal events is the accumulation of S-adenosyl-L-methionine that reaches intracellular pool concentrations allowing other redundant active S-adenosyltransferase genes to become active. During embryogenesis specific conformational-inducer proteins would block genes such as the gene for albumin from reheterochromatizing while alpha-fetoprotein gene becomes heterochromatized during subsequent cell cycles. This heterochromatin is formed with embryonic type proteins sensitive to ribosylation-induced conformational changes. The increase in synthesis of alpha-fetoprotein followed by a decrease as albumin synthesis increases during embryogenesis is predicted by the scheme.
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PMID:Derivation of a basic mechanism of control for embryonic genes as a specific subset. 128 99

The effects of dietary selenium deficiency and excess on N-nitrosomethylbenzylamine-(NMBA) induced esophageal neoplasia in rats and forestomach tumors in mice and the effects of dietary selenium on DNA adduct formation and on the activities of DNA adduct-repairing enzyme and oncogene expression in rat esophagus were investigated. The esophageal and forestomach tumors were induced by administration of NMBA by gavage with a total dose of 39 mg/kg body wt in rats and 12 mg/kg body wt in mice. Neither selenium dietary deficiency (Se < 0.02 ppm) nor selenium excess (2.0 ppm) showed any significant effect on the incidence of tumors or number of tumors per tumor-bearing animal. For the DNA adduct formation studies, rats were given a dose of NMBA intraperitoneally after six weeks on the different selenium-containing diets. No significant difference in the amount of the DNA adduct O6-methyldeoxyguanosine was found among the different selenium-treated groups. In a parallel group of rats that did not receive NMBA, the levels of esophageal O6-methyldeoxyguanosine DNA methyltransferase were not significantly altered by dietary selenium levels. The c-myc oncogene expression in rat esophagus was induced by the administration of NMBA (3 mg/kg body wt) by gavage once a week for eight weeks. Dietary selenium did not show any effects on its expression. On the basis of the results of these studies, dietary selenium has no effects in the NMBA-induced tumor model.
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PMID:Lack of effects of selenium on N-nitrosomethylbenzylamine-induced tumorigenesis, DNA methylation, and oncogene expression in rats and mice. 129 2

Methylation of a plasmid containing the SV40 promoter linked to the chloramphenicol acetyl transferase (CAT) gene, with either murine DNA methylase or methylase SssI results in inhibition of the expression of the reporter gene after transfection into cultured cells. Methylation of the plasmid with the methylases HhaI and HpaII has no effect on the expression of this gene. Protein-DNA interactions in the SV40 promoter are not affected by the presence of methylcytosine suggesting that inactivation results from the formation of an inactive chromatin structure that is dependent on the high CG content of the plasmid.
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PMID:Vector methylation inhibits transcription from the SV40 early promoter. 132 53

A 6.3 kb fragment of E.coli RFL57 DNA coding for the type IV restriction-modification system Eco57I was cloned and expressed in E.coli RR1. A 5775 bp region of the cloned fragment was sequenced which contains three open reading frames (ORF). The methylase gene is 1623 bp long, corresponding to a protein of 543 amino acids (62 kDa); the endonuclease gene is 2991 bp in length (997 amino acids, 117 kDa). The two genes are transcribed convergently from different strands with their 3'-ends separated by 69 bp. The third short open reading frame (186 bp, 62 amino acids) has been identified, that precedes and overlaps by 7 nucleotides the ORF encoding the methylase. Comparison of the deduced Eco57I endonuclease and methylase amino acid sequences revealed three regions of significant similarity. Two of them resemble the conserved sequence motifs characteristic of the DNA[adenine-N6] methylases. The third one shares similarity with corresponding regions of the PaeR7I, TaqI, CviBIII, PstI, BamHI and HincII methylases. Homologs of this sequence are also found within the sequences of the PaeR7I, PstI and BamHI restriction endonucleases. This is the first example of a family of cognate restriction endonucleases and methylases sharing homologous regions. Analysis of the structural relationship suggests that the type IV enzymes represent an intermediate in the evolutionary pathway between the type III and type II enzymes.
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PMID:Cloning and sequence analysis of the genes coding for Eco57I type IV restriction-modification enzymes. 133 61

Over 60 producing strains of restriction endonucleases type II have been found among 500 different strains, mostly Enterobacteriaceae. The strain Citrobacter freundii 4111 produces restriction endonuclease CfrBI, a new isoschisomer of StyI. The genes of the restriction-modification system CfrBI were located on the multicopy plasmid pZE8 containing the Co1E1-type replicon and cloned to E. coli K802. The deletion variant of 3.2-kb pZE8 which contains intact restriction-modification and a DNA fragment responsible for autonomous plasmid replication was selected among the recombinant plasmids. The strain with higher R. CfrBI production (at least 10,000,000 U/g cells, which is 500-fold higher than the wild strain) was constructed.
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PMID:[Plasmid localization and cloning of restriction modification genes from Citrobacter freundii 4111 strain]. 133 50


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