Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.1.1.37 (DNA methyltransferase)
 4,983 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

As a step toward the molecular elucidation of the putative replicational apparatus associated with the nuclear matrix, we have investigated the possible matrix association of several replicational related enzymes. In addition to the previously identified DNA polymerase alpha, DNA primase, 3'-5' exonuclease, RNase H, and DNA methylase were all recovered at significant levels (20-30% of total nuclear activity) in nuclear matrix isolated from regenerating rat liver during maximal in vivo replication (22 h post-hepatectomy). In contrast, DNA ligase was not detected on the nuclear matrix even though significant activity was present in isolated nuclei. Examination of the replicative dependency of these enzyme activities following partial hepatectomy revealed pre-replicative elevations which were distinct for each matrix-bound enzyme. A second late-replicative peak in DNA methylase is consistent with a role of this matrix-bound enzyme in the maintenance of the inheritable methylation pattern. Mild sonication resulted in a significant release of all of these activities except RNase H. A major portion of the matrix-solubilized DNA polymerase alpha, DNA primase, 3'-5' exonuclease, and DNA methylase activities cosedimented on sucrose gradients between approximately 8-12 S. Our results are consistent with the organization of at least a portion of these replicative enzymes into nuclear matrix-bound replicational complexes. We also propose a novel pre-replicative assembly model of the matrix-bound replicational apparatus in which DNA primase plays an initial and critical role.
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PMID:Pre-replicative association of multiple replicative enzyme activities with the nuclear matrix during rat liver regeneration. 302 82

Oxidation of DNA and its components can cause genetic mutations and chromosomal instability. These changes have generally been implicated in aging. Oxidation of the methyl group of thymidine residues in DNA is known to result in the formation 5-hydroxymethyl-2'-deoxyuridine (5HmdUrd). We have utilized Bacillus subtilis phage SPO1 DNA as a model of oxidatively damaged DNA. In this phage, all thymine (Thy) residues are replaced by 5-hydroxymethyluracil (5HmUra), but the species is naturally devoid of other oxidatively-induced DNA lesions. Particular attention was paid to the behavior of 5HmUra-containing DNA as a target for several enzymes employing DNA as substrate; restriction endonucleases, dam DNA methylase and T4 DNA ligase. We noticed that susceptibility of SPO1 DNA varied when different restriction endonucleases having 5HmUra in the restriction sites were tested. Endonucleolytic cleavage brought about Sau3A proceeded as effectively with SPO1 DNA as with conventional DNA (lambda phage). The same was true when the ligation of Sau3A sites was performed with T4 DNA ligase. In contrast, both endonucleolytic cleavage and ligation were slower in SPO1 DNA, compared with lambda phage, when Taq I and T4 DNA ligase were used for restriction and ligation, respectively. We also noticed that SPO1 phage does not naturally contain N6-methyladenine (N6MeAde) opposite 5HmUra, i.e., no hydrolysis of SPO1 DNA was observed when assessed with methylation-dependent restriction endonuclease DpnI. Our results show that the presence of 5HmUra in the respective site of DNA does not, per se, prevent the activity of restriction endonucleases, ligases or DNA methylases. These data support the view that oxidation of Thy to 5HmUra in target DNA does not necessarily result in substantial deterioration in the functions of DNA processing enzymes.
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PMID:Restriction, methylation and ligation of 5-hydroxymethyluracil-containing DNA. 786 75

This report completes a preliminary analysis of the sequence of the 330,740-bp chlorella virus PBCV-1 genome, the largest virus genome to be sequenced to date. The PBCV-1 genome is 57% the size of the genome from the smallest self-replicating organism, Mycoplasma genitalium. Analysis of 74 kb of newly sequenced DNA, from the right terminus of the PBCV-1 genome, revealed 153 open reading frames (ORFs) of 65 codons or longer. Eighty-five of these ORFs, which are evenly distributed on both strands of the DNA, were considered major ORFs. Fifty-nine of the major ORFs were separated by less than 100 bp. The largest intergenic distance was 729 bp, which occurred between two ORFs located in the 2.2-kb inverted terminal repeat region of the PBCV-1 genome. Twenty-seven of the 85 major ORFs resemble proteins in databases, including the large subunit of ribonucleotide diphosphate reductase, ATP-dependent DNA ligase, type II DNA topoisomerase, a helicase, histidine decarboxylase, dCMP deaminase, dUTP pyrophosphatase, proliferating cell nuclear antigen, a transposase, fungal translation elongation factor 3 (EF-3), UDP glucose dehydrogenase, a protein kinase, and an adenine DNA methyltransferase and its corresponding DNA site-specific endonuclease. Seventeen of the 153 ORFs resembled other PBCV-1 ORFs, suggesting that they represent either gene duplications or gene families.
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PMID:Analysis of 74 kb of DNA located at the right end of the 330-kb chlorella virus PBCV-1 genome. 935 47

Previous studies have shown that UV-induced binding of p21(WAF1) to PCNA through the PCNA-interacting protein (PIP) domain in p21(WAF1) promotes a switch from DNA replication to DNA repair by altering the PCNA protein complex. Here we show that the p33(ING1b) isoform of the ING1 candidate tumour suppressor contains a PIP domain. UV rapidly induces p33(ING1b) to bind PCNA competitively through this domain, a motif also found in DNA ligase, the DNA repair-associated FEN1 and XPG exo/endonucleases, and DNA methyltransferase. Interaction of p33(ING1b) with PCNA occurs between a significant proportion of ING1 and PCNA, increases more than tenfold in response to UV and is specifically inhibited by overexpression of p21(WAF1), but not by p16(MTS1), which has no PIP sequence. In contrast to wild-type p33(ING1b), ING1 PIP mutants that do not bind PCNA do not induce apoptosis, but protect cells from UV-induced apoptosis, suggesting a role for this PCNA-p33(ING1b) interaction in eliminating UV-damaged cells through programmed cell death. These data indicate that ING1 competitively binds PCNA through a site used by growth regulatory and DNA damage proteins, and may contribute to regulating the switch from DNA replication to DNA repair by altering the composition of the PCNA protein complex.
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PMID:UV-induced binding of ING1 to PCNA regulates the induction of apoptosis. 1168 5

The SinI DNA methyltransferase, a component of the SinI restriction-modification system, recognizes the sequence GG(A/T)CC and methylates the inner cytosine to produce 5-methylcytosine. Previously isolated relaxed-specificity mutants of the enzyme also methylate, at a lower rate, GG(G/C)CC sites. In this work we tested the capacity of the mutant enzymes to function in vivo as the counterpart of a restriction endonuclease, which can cleave either site. The viability of Escherichia coli cells carrying recombinant plasmids with the mutant methyltransferase genes and expressing the GGNCC-specific Sau96I restriction endonuclease from a compatible plasmid was investigated. The sau96IR gene on the latter plasmid was transcribed from the araBAD promoter, allowing tightly controlled expression of the endonuclease. In the presence of low concentrations of the inducer arabinose, cells synthesizing the N172S or the V173L mutant enzyme displayed increased plating efficiency relative to cells producing the wild-type methyltransferase, indicating enhanced protection of the cell DNA against the Sau96I endonuclease. Nevertheless, this protection was not sufficient to support long-term survival in the presence of the inducer, which is consistent with incomplete methylation of GG(G/C)CC sites in plasmid DNA purified from the N172S and V173L mutants. Elevated DNA ligase activity was shown to further increase viability of cells producing the V173L variant and Sau96I endonuclease.
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PMID:In vivo DNA protection by relaxed-specificity SinI DNA methyltransferase variants. 1884 37