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:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We utilized strains of Saccharomyces cerevisiae that exhibit high efficiency of synchrony of meiosis to examine several aspects of meiosis including sporulation, recombination, DNA synthesis, DNA polymerase I and II, and Mg2+-dependent alkaline DNases. The kinetics of commitment to intragenic recombination and sporulation are similar. The synthesis of DNA, as measured directly with diphenylamine, appears to precede the commitment to recombination. Both DNA polymerase I and II activities and total DNA-synthesizing activity in crude extracts increase two- to threefold before the beginning of meiotic DNA synthesis. Increases of 10- to 20-fold over mitotic levels are found for Mg2+-dependent alkaline DNase activity in crude extracts before and during the commitment to meiotic intragenic recombination. Of particular interest is the comparable increase in a nuclease under the control of the RAD52 gene; this enzyme has been identified by the use of antibody raised against a similar enzyme from Neurospora crassa. Since the RAD52 gene is essential for meiotic recombination, the nuclease is implicated in the high levels of recombination observed during meiosis. The effects observed in this report are meiosis specific since they are not observed in an alpha alpha strain.
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PMID:DNA polymerases, deoxyribonucleases, and recombination during meiosis in Saccharomyces cerevisiae. 639 7

The Saccharomyces cerevisiae rad6, rad18, and rad52 mutants exhibit DNA repair deficiencies and distinct mutator phenotypes. DNA replication past unrepaired spontaneous damage might contribute to the specificities of these mutators. Because REV3 is thought to encode a DNA polymerase that specializes in translesion synthesis, we determined the REV3 dependence of the rad mutator specificities. Spontaneous mutagenesis at a plasmid-borne SUP4-o locus was examined in isogenic strains having combinations of normal or mutant REV3 and RAD6, RAD18, or RAD52 alleles. For the rad6 and rad18 mutators, the mutation rate increase relied largely, but not exclusively, on REV3 whereas the rad52 mutator was entirely REV3 dependent. The influence of REV3 on the specificity of the rad6 mutator differed markedly depending on the mutational class examined. However, the requirement of rev3 for the production of G.C-->T.A transversions by the rad18 mutator, which induces only these substitutions, was similar to that for rad6-mediated G.C-->T.A transversion. This supports a role for the Rad6-Rad18 protein complex in the control of spontaneous mutagenesis. The available data imply that the putative Rev3 polymerase can process a variety of spontaneous DNA lesions that normally are substrates for error-free repair.
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PMID:Specificities of the Saccharomyces cerevisiae rad6, rad18, and rad52 mutators exhibit different degrees of dependence on the REV3 gene product, a putative nonessential DNA polymerase. 749 27

Genetic control of mutagenesis by the base analog 6-N-hydroxylaminopurine (HAP) was studied in a set of isogenic yeast strains carrying null or point mutations in DNA repair and replication genes. Null alleles of the PMS1, RAD6, REV3 and RAD52 genes did not affect HAP mutagenesis. Defects in 3'- > 5' exonucleases associated with DNA polymerases epsilon and delta led to 2- to 3-fold increases in HAP-induced forward Can(r) mutant frequency. A similar increase was observed for FOAr mutants but only in the strain with a defective exonuclease of the polymerase epsilon (mutation pol2-4). The polymerase epsilon mutations, pol2-9 and pol2-18, which lead to temperature-sensitivity, and pol2-1 (insertion of URA3 at the position coding for amino acid 1134 in the POL2 gene) substantially reduced HAP mutagenesis. The polymerase delta mutation, cdc2-2, slightly reduced HAP mutagenesis. Enhanced proofreading was not the cause of the antimutator effect in the pol2-18 bearing strain, inasmuch as antimutator effect was observed in the pol2-4,18 mutant strain lacking proofreading. From the data obtained, we conclude that both DNA polymerase epsilon and delta participate in mutation generation by HAP.
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PMID:Base analog 6-N-hydroxylaminopurine mutagenesis in the yeast Saccharomyces cerevisiae is controlled by replicative DNA polymerases. 870 Jan 80

We have investigated the effects of mismatch repair on 1-to 61-bp deletions in the yeast Saccharomyces cerevisiae. The deletions are likely to involve unpaired loop intermediates resulting from DNA polymerase slippage. The mutator effects of mutations in the DNA polymerase delta (POL3) gene and the recombinational repair RAD52 gene were studied in combination with mismatch repair defects. The pol3-t mutation increased up to 1000-fold the rate of extended (7-61 bp) but not of 1-bp deletions. In a rad52 null mutant only the 1-bp deletions were increased (12-fold). The mismatch repair mutations pms1, msh2 and msh3 did not affect 31- and 61-bp deletions in the pol3-t but increased the rates of 7- and 1-bp deletions. We propose that loops less than or equal to seven bases generated during replication are subject to mismatch repair by the PMS1, MSH2, MSH3 system and that in cannot act on loops > or = 31 bases. In contrast to the pol3-t, the enhancement of 1-bp deletions in a rad52 mutant is not altered by a pms1 mutation. Thus, mismatch repair appears to be specific to errors of DNA synthesis generated during semiconservative replication.
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PMID:The prevention of repeat-associated deletions in Saccharomyces cerevisiae by mismatch repair depends on size and origin of deletions. 884 47

The RAD27/RTH1 gene of Saccharomyces cerevisiae encodes a structural and functional homolog of the 5'-3' exonuclease function of Escherichia coli DNA polymerase I. Four alleles of RAD27 were recovered in a screen for hyper-recombination, a phenotype also displayed by polA mutants of E.coli. All four rad27 mutants showed similar high levels of mitotic recombination, but varied in their growth rate at various temperatures, and sensitivity to the DNA damaging agent methyl methane sulfonate. Dependence of viability of rad27 strains on recombination was determined by crossing a strain containing a null allele of RAD27 to strains containing a mutation in either the RAD1, RAD50, RAD51, RAD52, RAD54, RAD55, RAD57, MRE11, XRS2 or RAD59 gene. In no case were viable spore products recovered that contained both mutations. Elimination of the non-homologous end-joining pathway did not affect the viability of a rad27 strain. This suggests that lesions generated in the absence of RAD27 must be processed by homologous recombination.
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PMID:Homologous recombination is required for the viability of rad27 mutants. 983 87

Pol32 is a subunit of Saccharomyces cerevisiae DNA polymerase delta required in DNA replication and repair. To gain insight into the function of Pol32 and to determine in which repair pathway POL32 may be involved, we extended the analysis of the pol32delta mutant with respect to UV and methylation sensitivity, UV-induced mutagenesis; and we performed an epistasis analysis of UV sensitivity by combining the pol32delta with mutations in several genes for postreplication repair (RA D6 group), nucleotide excision repair (RAD3 group) and recombinational repair (RAD52 group). These studies showed that pol32delta is deficient in UV-induced mutagenesis and place POL32 in the error-prone RAD6/ REV3 pathway. We also found that the increase in the CAN1 spontaneous forward mutation of different rad mutators relies entirely or partially on a functional POL32 gene. Moreover, in a two-hybrid screen, we observed that Pol32 interacts with Srs2, a DNA helicase required for DNA replication and mutagenesis. Simultaneous deletion of POL32 and SRS2 dramatically decreases cellular viability at 15 degrees C and greatly increases cellular sensitivity to hydroxyurea at the permissive temperature. Based on these findings, we propose that POL32 defines a link between the DNA polymerase and helicase activities, and plays a role in the mutagenic bypass repair pathway.
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PMID:POL32, a subunit of the Saccharomyces cerevisiae DNA polymerase delta, defines a link between DNA replication and the mutagenic bypass repair pathway. 1112 76

The Pol32 subunit of S. cerevisiae DNA polymerase (Pol) delta plays an important role in replication and mutagenesis. Here, by measuring the CAN1 forward mutation rate, we found that either POL32 or REV3 (which encodes the Pol zeta catalytic subunit) inactivation produces overlapping antimutator effects against rad mutators belonging to three epistasis groups. In contrast, the msh2Delta pol32Delta double mutant exhibits a synergistic mutator phenotype. Can(r) mutation spectrum analysis of pol32Delta strains revealed a substantial increase in the frequency of deletions and duplications (primarily deletions) of sequences flanked by short direct repeats, which appears to be RAD52 and RAD10 independent. To better understand the pol32Delta and rev3Delta antimutator effects in rad backgrounds and the pol32Delta mutator effect in a msh2Delta background, we determined Can(r) mutation spectra for rad5Delta, rad5Delta pol32Delta, rad5Delta rev3Delta, msh2Delta, msh2Delta pol32Delta, and msh2Delta rev3Delta strains. Both rad5Delta pol32Delta and rad5Delta rev3Delta mutants exhibit a reduction in frameshifts and base substitutions, attributable to antimutator effects conferred by the pol32Delta and rev3Delta mutations. In contrast, an increase in these two types of alterations is attributable to a synergistic mutator effect between the pol32Delta and msh2Delta mutations. Taken together, these observations indicate that Pol32 is important in ensuring genome stability and in mutagenesis.
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PMID:Pol32, a subunit of Saccharomyces cerevisiae DNA polymerase delta, suppresses genomic deletions and is involved in the mutagenic bypass pathway. 1197 97

The DNA synthesis associated with recombinational repair of chromosomal double-strand breaks (DSBs) has a lower fidelity than normal replicative DNA synthesis. Here, we use an inverted-repeat substrate to monitor the fidelity of repair of a site-specific DSB. DSB induction made by the HO endonuclease stimulates recombination >5000-fold and is associated with a >1000-fold increase in mutagenesis of an adjacent gene. We demonstrate that most break-repair-induced mutations (BRIMs) are point mutations and have a higher proportion of frameshifts than do spontaneous mutations of the same substrate. Although the REV3 translesion DNA polymerase is not required for recombination, it introduces approximately 75% of the BRIMs and approximately 90% of the base substitution mutations. Recombinational repair of the DSB is strongly dependent upon genes of the RAD52 epistasis group; however, the residual recombinants present in rad57 mutants are associated with a 5- to 20-fold increase in BRIMs. The spectrum of mutations in rad57 mutants is similar to that seen in the wild-type strain and is similarly affected by REV3. We also find that REV3 is required for the repair of MMS-induced lesions when recombinational repair is compromised. Our data suggest that Rad55p/Rad57p help limit the generation of substrates that require pol zeta during recombination.
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PMID:The roles of REV3 and RAD57 in double-strand-break-repair-induced mutagenesis of Saccharomyces cerevisiae. 1245 56

Resting cells experience mutations without apparent external mutagenic influences. Such DNA replication-independent mutations are suspected to be a consequence of processing of spontaneous DNA lesions. Using experimental systems based on reversions of frameshift alleles in Saccharomyces cerevisiae, we evaluated the impact of defects in DNA double-strand break (DSB) repair on the frequency of replication-independent mutations. The deletion of the genes coding for Ku70 or DNA ligase IV, which are both obligatory constituents of the non-homologous end joining (NHEJ) pathway, each resulted in a 50% reduction of replication-independent mutation frequency in haploid cells. Sequencing indicated that typical NHEJ-dependent reversion events are small deletions within mononucleotide repeats, with a remarkable resemblance to DNA polymerase slippage errors. Experiments with diploid and RAD52- or RAD54-deficient strains confirmed that among DSB repair pathways only NHEJ accounts for a considerable fraction of replication-independent frameshift mutations in haploid and diploid NHEJ non-repressed cells. Thus our results provide evidence that G(0) cells with unrepressed NHEJ capacity pay for a large-scale chromosomal stability with an increased frequency of small-scale mutations, a finding of potential relevance for carcinogenesis.
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PMID:Non-homologous end joining as an important mutagenic process in cell cycle-arrested cells. 1272 93

Mutations of chromosome replication genes can be one of the early events that promote genomic instability. Among genes that are involved in chromosomal replication, DNA polymerase alpha is essential for initiation of replication and lagging-strand synthesis. Here we examined the effect of two mutations in S. cerevisiae POL1, pol1-1 and pol1-17, on a microsatellite (GT)(16) tract. The pol1-17 mutation elevated the mutation rate 13-fold by altering sequences both inside and downstream of the (GT)(16) tract, whereas the pol1-1 mutation increased the mutation rate 54-fold by predominantly altering sequences downstream of the (GT)(16) tract in a RAD52-dependent manner. In a rad52 null mutant background pol1-1 and pol1-17 also exhibited different plasmid and chromosome loss phenotypes. Deletions of mismatch repair (MMR) genes induce a differential synergistic increase in the mutation rates of pol1-1 and pol1-17. These findings suggest that perturbations of DNA replication in these two pol1 mutants are caused by different mechanisms, resulting in various types of mutations. Thus, mutations of POL1 can induce a variety of mutator phenotypes and can be a source of genomic instability in cells.
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PMID:Genomic instability induced by mutations in Saccharomyces cerevisiae POL1. 1450 18


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