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)

The antibiotic bleomycin stimulates deoxyribonucleic acid (DNA) synthesis in toluene-treated Escherichia coli cells. The increase in synthesis is linear with bleomycin concentration. Bleomycin-stimulated DNA synthesis is independent of replication and dependent on DNA polymerase I. Replication is spared as the DNA polymerase I-dependent DNA synthesis increases. Bleomycin does not appear to have any effect on purified E. coli DNA polymerases I or II. Our results suggest that bleomycin causes nicking of the bacterial chromosome with subsequent DNA synthesis catalyzed by DNA polymerase I.
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PMID:Effect of bleomycin on deoxyribonucleic acid synthesis in toluene-treated Escherichia coli cells. 5 40

NAD prevents a DNA repair-type synthesis that is dependent on polymerase I in toluene-treated, X-irradiated Bacillus subtilis. In unirradiated preparations, NAD had little effect on an ATP-dependent, semiconservative synthesis but partially inhibited a repair-type synthesis. In a mutant lacking polymerase I (polA1-), the presence of NAD did not affect dTTP utilization in DNA synthesis. Nicotinamide mononucleotide (NMN) partially reverses the NAD inhibition of repair-type DNA synthesis. NADP and FAD were ineffective as substitutes for NAD. Since NAD is the cofactor for polynucleotide ligase in Bacillus subtilis and NMN is known to discharge AMP from the active AMP ligase complex, it is proposed that activation of DNA ligase reduces dTMP incorporation by reducing sites for, or limiting DNA polymerase I action.
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PMID:Depression by NAD of x-ray-induced repair-type DNA synthesis in toluene-treated Bacillus subtilis. 16 15

In toluene-treated Escherichia coli incision breaks accumulate during post-irradiation incubation in the presence of adenosine 5'-triphosphate (ATP). It is shown that incised deoxyribonucleic acid (DNA) is converted to high-molecular-weight DNA during reincubation in the presence of the four deoxyribonucleoside triphosphates (dNTP's) and nicotinamide adenine dinucleotide (NAD). This restitution process is ATP independent and N-ethylmaleimide insensitive and takes place only in polA+ strains. It is defective in strains carrying a mutation in the 5' leads to 3' exonucleolytic activity associated with DNA polymerase I. Repair of accumulated incision breaks differs from repair in which all the steps of the excision repair process occur simultaneously or in rapid succession. The latter is observed if toluene-treated E. coli are incubated immediately after irradiation in the presence of the four dNTP's, NAD, and ATP. It is shown that under these conditions dimer excision occurs to a larger extent than during repair of accumulated incision breaks and that, except in strains defective in polynucleotide ligase, incision breaks do not accumulate. This consecutive mode of repair is detectable in polA+ strains and at low doses also in polA mutants.
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PMID:Two modes of excision repair in toluene-treated Escherichia coli. 16 27

Toluene-treated Escherichia coli mutants have been used to study the roles of deoxyribonucleic acid (DNA) polymerases I, II, and III, and of DNA ligase in repair synthesis and strand rejoining following X-irradiation. In cells possessing all three DNA polymerases, both a greater amount of repair synthesis ("exaggerated" repair synthesis) and failure of ligation are observed when DNA ligase activity is inhibited. In a mutant lacking the polymerizing activity of DNA polymerase I, exaggerated repair synthesis is not observed, and strand rejoining does not occur even if DNA ligase is fully activated. In a mutant possessing the polymerizing activity of DNA polymerase I but lacking its 5'leads to 3' exonuclease activity, exaggerated repair synthesis is minimal. After irradiation, DNA polymerases II and III are capable of carrying out an adenosine 5'-triphosphate-dependent repair synthesis,but rejoining of strand breaks does not occur and exaggerated synthesis is not seen whether DNA ligase is active or not. These results suggest that DNA polymerase I and DNA ligase act together to limit repair synthesis after X irradiation and that both are necessary in toluene-treated cells for strand rejoining. DNA polymerases II and III apparently cannot complete chain elongation and gap filling, and therefore repair carried out by these enzymes does not respond to ligase action.
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PMID:Role of deoxyribonucleic acid polymerases and deoxyribonucleic acid ligase in x-ray-induced repair synthesis in toluene-treated Escherichia coli K-12. 17 4

Escherichia coli made permeable by treatment with toluene can perform a mode of DNA synthesis that is stimulated by ultraviolet radiation and closely resembles the resynthesis step of excision repair. If ultraviolet-irradiated toulene-treated cells are incubated in an assay mixture with ATP but without the four deoxyribonucleoside triphosphates (dNTPs) or NAD, accumulations of single-strand breaks in the DNA are detected by alkaline sucrose gradient analysis. A second incubation with the dNTP'S and NAD but without ATP produces nonconservative DNA synthesis in strains with normal levels of DNA polymerase I. However, in PolA strains, ATP must be present during the second incubation in order to produce measurable amounts of ultraviolet-stimulated DNA synthesis. These results suggest that in strains deficient in DNA polymerase I there may be two ATP-dependent steps in this repair pathway, one required for incision and one associated with resynthesis.
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PMID:The ATP dependence of the incision and resynthesis steps of excision repair. 18 56

Escherichia coli cells whose chromosome replication has been terminated in vivo, either by growth into stationary phase or by incubation of a mutant carrying a temperature-sensitive initiation mutation under restrictive conditions, are inactive in in vitro DNA synthesis as measured in toluene-treated cells. Addition of the non-ionic detergent Triton X-100 to such inactive systems results in a marked stimulation of ATP-dependent in vitro DNA synthesis. This Triton-stimulated DNA synthesis appears to proceed by a semi-conservative mechanism, in that DNA synthesized in vitro in the presence of a density labeled precursor bands in CsCl equilibrium centrifugation at a hybrid density. Neutral sucrose gradient centrifugation demonstrates that most of this hybrid material exhibits a molecular weight in excess of 1 X 10(7). Triton-stimulated synthesis requires the presence of DNA polymerase III, as does normal in vivo replication. We show here, however, several anomalous properties of the DNA synthesis in the Triton/toluene system. In particular, Triton-stimulated synthesis is absent in cells harboring a recB mutation which lack the ATP-dependent exonuclease V, an enzyme implicated in recombinational repair synthesis in vivo. Furthermore, the ATP requirement for Triton-stimulated synthesis is relatively non-sepcific, and a variety of nucleoside triphosphates can effectively substitute for ATP. Finally, despite their high molecular weight in neutral sucrose gradient centrifugation, Triton-stimulated DNA synthesis generates DNA molecules of low molecular weight (less than 500 000) as determined by alkaline sucrose gradient centrifugation. In contrast, DNA synthesis in the normal toluene-treated cell system is not dependent on recB activity, shows a nearly absolute requirement for ATP which cannot be replaced by other nucleoside triphosphates, and produces molecules of far greater molecular weight as measured on alkaline sucrose gradients. Taken altogether the data strongly suggest that Triton activates an unusual form of DNA synthesis in toluene-treated cells which shows both repair and replicative aspects. These results caution against the use of Triton-activated toluene-treated cells system, for studying simple replicative DNA synthesis.
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PMID:Triton X-100 activates nucleoside triphosphate-dependent, recBC-dependent DNA synthesis in toluene-treated Escherichia coli. 31 67

Removal of interstrand cross-linked from DNA was examined in Escherichia coli permeabilized by treatment with toluene. Under these conditions, the reaction requires ATP and Mg2+, and the mechanism appears to be similar to that occurring in whole cells. Under optimum conditions, the rate constant was 0.06 min-1. Genetical, physical, and biochemical analysis of the repair process suggest the following mechanism. In an ATP-dependent reaction, the uvrA and uvrB gene products cleave a phosphodiester bond on the 5' side of one arm of the cross-link, producing a 3'-OH terminus. Subsequently, DNA polymerase I (5'-3' exonuclease activity) makes a second strand cut on the 3' side of the cross-link in the same DNA strand, completing removal of the covalent link between complementary strands. The second reaction did not occur in a uvrD- strain, which had normal levels of DNA polymerizing activity. The uvrD gene may regulate the specificity or activity of the 5'-3' exonuclease of DNA polymerase I in vivo.
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PMID:Role of ATP in removal of psoralen cross-links from DNA of Escherichia coli permeabilized by treatment with toluene. 33 87

DNA synthesis after ultraviolet irradiation is low in wild type toluene-treated cells. The level of repair incorporation is greater in strains deficient in DNA polymerase I. The low level of repair synthesis is attributable to the concerted action of DNA polymerase I and polynucleotide ligase. Repair synthesis is stimulated by blocking ligase activity with the addition of nicotinamide mononucleotide (NMN) or the use of a ligase temperature-sensitive mutant. NMN stimulation is specific for DNA polymerase I-mediated repair synthesis, as it is absent in isogenic strains deficient in the polymerase function or the 5' leads to 3' exonuclease function associated with DNA polymerase I. DNA synthesis that is stimulated by NMN is proportional to the ultraviolet exposure at low doses, nonconservative in nature, and is dependent on the uvrA gene product but is independent of the recA gene product. These criteria place this synthesis in the excision repair pathway. The NMN-stimulated repair synthesis requires ATP and is N-ethylmaleimide-resistant. The use of NMN provides a direct means for evaluating the involvement of DNA polymerase I in excision repair.
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PMID:DNA polymerase I-mediated ultraviolet repair synthesis in toluene-treated Escherichia coli. 34 Apr 56

Toluene treated cells have been used to study the processes of DNA synthesis and DNA degradation in ultra-violet irradiated Escherichia coli K12. Synthesis and degradation are both shown to occur extensively if polynucleotide ligase is inhibited, and to occur to a much lesser extent if ligase activity is optimal. Extensive UV-induced DNA synthesis in toluene-treated cells requires ATP for the initial incision step, and DNA polymerase I. Extensive degradation also depends on the early ATP-dependent incision step, and the subsequent degradation shows a partial requirement for ATP. Curtailment of degradation by ligase requires DNA polymerase activity, but is not dependent upon DNA polymerase I. Apparently this process can be carried out with equal facility by either DNA polymerase II or polymerase III. These observations suggest that extensive DNA polymerase I-dependent repair synthesis and extensive DNA degradation are facets of two divergent pathways of excision repair, both of which depend upon the early uvrABC determined ATP-dependent incision step.
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PMID:DNA synthesis and degradation in UV-irradiated toluene treated cells of E. coli K12: the role of polynucleotide ligase. 34 Sep 17

We have examined the role of the uvrC gene in UV excision repair by studying incision, excision, repair synthesis, and DNA strand reformation in Escherichia coli mutants made permeable to nucleoside triphosphates by toluene treatment. After irradiation, incisions occur normally in uvrC cells in the presence of nicotinamide mononucleotide (NMN), a ligase-blocking agent, but cannot be detected otherwise. We conclude that repair incisions are followed by a ligation event in uvrC mutants, masking incision. However, a uvrC polA12 mutant accumulates incisions only slightly less efficiently than a polA12 strain without NMN. Excision of pyrimidine dimers is defective in uvrC mutants (polA(+) or polA12) irrespective of the presence or absence of NMN. DNA polymerase I-dependent, NMN-stimulated repair synthesis, which is demonstrable in wild-type cells, is absent in uvrC polA(+) cells, but the uvrC polA12 mutant exhibits a UV-specific, ATP-dependent repair synthesis like parental polA12 strains. A DNA polymerase I-mediated reformation of high-molecular-weight DNA takes place efficiently in uvrC polA(+) mutants after incision accumulation, and the uvrC polA12 mutant shows more reformation than the polA12 strain after incision. These results indicate that normal incision occurs in uvrC mutants, but there appears to be a defect in the excision of pyrimidine dimers, allowing resealing via ligation at the site of the incision. The lack of NMN-stimulated repair synthesis in uvrC polA(+) cells indicates that incision is not the only requirement for repair synthesis.
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PMID:uvrC gene function in excision repair in toluene-treated Escherichia coli. 36 20


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