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)

Double mutants of Escherichia coli were constructed by combining DNA thermosensitive mutations affecting either DNA initiation (DnaA) or elongation (DnaB) with the Pol A1 mutation, which abolishes DNA polymerase activity. Incorporation of labeled deoxynucleoside triphosphates was studied in these mutants using toluene-treated cells. This incorporation was found to be exactly correlated with the capacity of the mutants to synthesize DNA in vivo.
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PMID:On the process of cellular division in Escherichia coli. V. Incorporation of deoxynucleoside triphosphates by DNA thermosensitive mutants of Escherichia coli also lacking DNA polymerase activity. 494 81

Bleomycin (BLM) is an antitumor drug which interacts with and damages DNA. We have reported a repair response dependent on DNA polymerase I in toluene-treated Escherichia coli. We report here that DNA polymerase III can also catalyze a repair response in toluene-treated E. coli following exposure to BLM. Polymerase III-mediated synthesis differs because it is ATP-dependent, whereas polymerase I-mediated repair synthesis is not. Polymerase III repair synthesis is independent of replicative synthesis, as demonstrated in a polA-, dnaBts strain, or use of Novobiocin to inhibit replication, and replication persists in the presence of repair synthesis. It appears that ATP-dependent repair synthesis in response to BLM is also present in polA+ strains. Repair synthesis does not require the uvrA gene product.
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PMID:DNA polymerase III-dependent repair synthesis in response to bleomycin in toluene-treated Escherichia coli. 616 Mar 70

Caffeine inhibited DNA synthesis in toluene-treated Escherichia coli K12 strains to the same extent as in intact cells using the incorporation of [3H]thymidine as a measure of DNA synthesis. The inhibition was found to be competitive with ATP, and it was not influenced by the concentrations of deoxynucleoside triphosphates to any extent. When caffeine was added together with other DNA synthesis inhibitors such as novobiocin, nalidixic acid or actinomycin D, the inhibition in all cases was non-additive. It is suggested that caffeine inhibits one of the ATP-requiring enzymes in the DNA replication machinery, possibly DNA polymerase III or one of the DNA helicases.
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PMID:Mechanism of caffeine-induced inhibition of DNA synthesis in escherichia coli. 633 73

In Escherichia coli made permeable to nucleotides by toluene treatment, a DNA polymerase I-directed repair synthesis is induced by exposure to X rays. This repair synthesis may be amplified and easily measured through inhibition of DNA ligase action. In an effort to learn more of the relationship between X-ray-induced strand breaks in cellular DNA and the extent of this repair synthesis, experiments designed to compare the influence of radioprotectors on both strand-break production and repair synthesis have been carried out. The results show that cysteamine, sodium formate, and glycerol not only protect against strand breaks but also reduce DNA polymerase I-directed repair synthesis. However, I-, an efficient hydroxyl radical scavenger, is not as effective a protective agent against strand breaks and does not measurably affect repair synthesis in our system.
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PMID:The effects of radioprotectors on DNA polymerase I-directed repair synthesis and DNA strand breaks in toluene-treated and X-irradiated Escherichia coli. 634 66

Gamma-irradiation of Escherichia coli cells made permeable to deoxynucleoside triphosphates (dNTP) by toluene induces a repair-type DNA synthesis. As previous studies have shown ATP stimulates this DNA synthesis; we studied the mechanism of the ATP effect by analyzing the kinetics of nucleotide incorporation at various dNTP concentrations. The V values of the DNA repair synthesis rise with increasing dose (0-50 Gy); nonirradiated cells showed a negligible nucleotide incorporation. The apparent Michaelis constant KM for dNTP in the assay was 83-143 microM and the value was much higher than for a DNA polymerase reaction in vitro. ATP stimulated the DNA synthesis with concomitant decrease of KM yet unchanged V values. Similar results were obtained with a rec BC strain. We propose that the ATP effect is due to a greater affinity of dNTPs to the DNA polymerase, possibly by a stabilisation of the structural integrity of the complex DNA with repair enzymes. Activation of exonucleases by ATP could be excluded. Addition of NAD to the reaction mixture inhibits the DNA synthesis possibly by activation of ligase which closes the nicks in the DNA strand.
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PMID:Mechanism of the ATP effect in the DNA repair synthesis of gamma-irradiated Escherichia coli cells. 698 3

Alkylatio of Escherichia coli DNA that have been made permeable to nucleotides by toluene treatment results in the expression of DNA polymerase I-directed repair synthesis. The system only permits measurement of DNA polymerase I-directed repair synthesis. The latter is not observed in mutant cells deficient in this polymerase. DNA ligation is intentionally prevented by the addition of the inhibitor, nicotinamide mononucleotide. MNU, ENU and MMS elicit DNA polymerase I-directed repair synthesis. MNU and MMS are especially potent in this regard, while EMS is a poor inducer of DNA polymerase I activity in permeabilized cells. The natural compound para-aminobenzoic acid itself (0,0002 mM - 20 mM) doesn't induce DNA polymerase I-directed repair synthesis. However, when PABA is used in complex with alkylating agents as the inducers, the repair synthesis increased 2,0, 1,2 and 2,8 times for MNU, ENU and EMS, respectively, as compared to that elicited by "pure" mutagens. The increasing of DNA repair synthesis in permeabilized bacteria in the experiments with PABA may serve as the foundation for its reparagenic activity. The latter was discovered previously by the authors in experiments on mutagenesis of bacterial cells.
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PMID:[Genetic activity of para-aminobenzoic acid. The intensification of DNA polymerase I-dependent repair induced by chemical mutagens in toluene-treated Escherichia coli cells]. 704 62

Although DNA polymerase fidelity has been mainly ascribed to Watson-Crick hydrogen bonds, two nonpolar isosteres for thymine (T) and adenine (A)--difluorotoluene (F) and benzimidazole (Z) --effectively mimic their natural counterparts in polymerization experiments with pol I (KF exo-) [JC Morales and ET Kool. Nature Struct Biol, 5, 950-954, 1998]. By ab initio quantum chemical gas phase methods (HF/6-31G* and MP2/6-31G**) and a solvent phase method (CPCM-HF/6-31G**), we find that the A-F interaction energy is 1/3 the A-T interaction energy in the gas phase and unstable in the solvent phase. The F-Z and T-Z interactions are very weak and T-Z is quite unstable in the solvent. Electrostatic solvation energy calculations on F, Z and toluene yield that Z is two times, and F and toluene are five times, less hydrophilic than the natural bases. Of the new "base-pairs" (F-Z, T-Z, and F-A), only F-A formed an A-T-like arrangement in unconstrained optimizations. F-Z and T-Z do not freely form planar arrangements, and constrained optimizations show that large amounts of energy are required to make these pairs fit the exact A-T geometry, suggesting that the polymerase does not require all bases to conform to the exact A-T geometry. We discuss a model for polymerase/nucleotide binding energies and investigate the forces and conformational range involved in the polymerase geometrical selection.
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PMID:Interaction and solvation energies of nonpolar DNA base analogues and their role in polymerase insertion fidelity. 1044 97

We have isolated a mutant of Bacillussubtilis deficient in DNA polymerase I, denominated polA42, which shows a reduced ability to repair the damage to DNA by UV radiation, MMS and mitomycin C;the ability to perform recombination is not appreciably impaired.DEAE cellulose chromatography allows the separation of polymerases I and II from the parental strain;a simple procedure is also described which allows to separate rapidly the polymerases II and III of the mutant strain. The three separated polymerases have similar catalytic properties but they can be distinguished for their sensitivity to inhibitors: PCMB inhibits polymerases II and III but not polymerase I; HPUra inhibits only polymerase III. All three enzymes are unaffected by nalidixate. The DNA synthesis occurring in cells of the polA42 strain permeabilized with toluene is inhibited by nalidixate, whereas the synthesis occurring in polA(+) toluenized cells is unaffected by the drug. The polA gene has been mapped by transduction and localized between the phe(12) and argA(3) genes.
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PMID:Properties of a Bacillus subtilis strain lacking DNA polymerase I. 1079 79

The deoxyadenosine derivative tethering the phenyl group at N6 of deoxyadenosine (A(phe)) was previously found to have a property to stack strongly with adjacent nucleotide bases in a DNA duplex. On the other hand, it was also demonstrated that DNA polymerases selectively incorporated dTTP opposite A(phe) in a template DNA strand. These observations suggest that the conformation of A(phe) in solution differs from that during the DNA polymerase reaction. Here, the chemical modifications of thymine bases in a DNA duplex by KMnO(4) and CMCT (1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide metho-p-toluene sulfonate) were examined, and it was revealed that the thymine base opposite A(phe) was efficiently flipped out of the DNA helix as much as that in a single-stranded DNA.
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PMID:The base-pairing ability of the base pair-mimic nucleosides. 1802 91


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