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)

Inhibitors of DNA polymerase alpha (aphidicolin, phosphonoacetic acid, phosphonoformic acid) efficiently inhibit initiator-induced amplification of SV40 DNA sequences in the SV40-transformed Chinese hamster cell line CO631. Amplification is also inhibited by various protease inhibitors (antipain, leupeptin, aprotinin, alpha-I-antitrypsin, epsilon-amino-caproic acid, soy-bean protease inhibitor), by the non-initiating but DNA-damaging agent caffeine, and by sodium butyrate, which inhibits DNA synthesis by histone modification. In contrast, an inhibitor of topoisomerase II, nalidixic acid, enhances amplification when applied simultaneously with initiating treatment. This latter compound does not induce amplification when applied without initiator. Cycloheximide induces DNA amplification in the same way as chemical and physical carcinogens. This amplification can still be observed when protein synthesis is completely blocked. The data suggest a complex mechanism of selective DNA amplification. The possible involvement of proteases leading to a functional modification of DNA polymerase alpha is discussed.
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PMID:Selective DNA-amplification induced by carcinogens (initiators): evidence for a role of proteases and DNA polymerase alpha. 389 46

Extracts of DNA polymerase I defective Escherichia coli infected with phage T4 contain an exonuclease activity that removes thymine dimers from UV-irradiated DNA previously nicked with T4 UV endonuclease. This activity is not expressed if cells are infected in the presence of chloramphenicol. The enzyme has a requirement for divalent cation and is not affected by caffeine, but excision is inhibited in the presence of proflavine. The enzyme is present in all phage T4 mutants thus far examined, including 25 UV-sensitive mutants isolated during the course of the experiments, all of which are defective in the v gene. A similar activity can be detected in cells infected with phages T2, T3, and T6, but not in cells infected with phage T7.
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PMID:Excision of thymine dimers in vitro by extracts of bacteriophage-infected Escherichia coli. 459 98

Since caffeine reorganizes the DNA replicating system, with several consequences, we studied the effect of caffeine on the DNA replication which normally occurs on or near the nuclear matrix in a variety of eukaryotic cells. When HeLa cells, treated with or without the DNA-damaging agent, neocarzinostatin, were postincubated in the presence or absence of caffeine and then pulse-labeled with [3H]thymidine, the DNA remaining tightly associated with the matrix was enriched in the newly synthesized DNA at the same level as that seen in untreated cells. The nuclear matrix-bound DNA polymerase alpha activity was also the same in these cells. Therefore, in the presence of caffeine, DNA replication, with or without DNA damage, also occurs on or near the nuclear matrix, as is the case in normal DNA replication.
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PMID:Caffeine-induced reorganization of DNA replicating system occurs on or near nuclear matrix in HeLa cells. 624 Sep 82

The exact sites at which a number of drugs inhibit the nick translation of DNA by E.coli DNA polymerase-I have been pinpointed. In order to do this, a method has been developed for sequencing double-stranded plasmid DNA from the site of a specifically induced nick. The initial experiments have concentrated on analysis of drug inhibition of nick translation in a 200 nucleotide region near the Eco Rl origin of pBR313. Many drugs were found to inhibit nick translation in a highly sequence specific manner. For actinomycin D, significant inhibition occurred at just four sites in the nucleotide sequence under test and only one sequence (pGpCpGpCpGpGp) gave really strong inhibition. Distamycin A gave a different pattern of inhibition with particularly strong stops in just two of the many A-T rich regions in the DNA. Experiments with caffeine suggest that factors in addition to primary sequence are important in determining where major inhibition occurs.
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PMID:Selective binding of actinomycin D and distamycin A to DNA. 629 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

The mutation frequency of DNA polymerase mutants of phage T4 treated with ethyl methanesulfonate (EMS) then incubated in the presence and absence of caffeine was studied using an rII reversion system. The DNA polymerase mutation is shown to be antimutagenic for EMS induction of reversions which occur by a GC to AT transition. Caffeine acts as a comutagen for the induction by EMS of mutant phages and produces a significant increase in the frequency of reversions from rII to r+. Caffeine is slightly mutagenic for the phage strain carrying the wild type polymerase and inhibits the action of the 3' leads to 5' exonuclease function of T4 DNA polymerase as measured in vitro. These findings suggest that caffeine acts by directly influencing nucleotide selection or the editing function of the DNA polymerase.
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PMID:Caffeine as a comutagen for ethylmethanesulfonate in strains of phage T4. 693 94

Caffeine inhibits the activity of DNA polymerase I (E. coli) and its proteolytic large fragment in in vitro DNA replication system. DNA polymerase from Micrococcus luteus is also equally inhibited by caffeine. The extent of inhibition was more with the activated adenovirus, T4 and calf thymus DNA than with synthetic DNA template-primers. Results obtained from time-course studies indicated that caffeine inhibition reached maximum by 30 min of incubation. Enzyme kinetic studies showed that inhibition was competitive with respect to DNA template.
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PMID:Caffeine inhibits DNA polymerase I from Escherichia coli: studies in vitro. 703 55

Monobutyryl adenosine 3',5' monophosphate (mbcAMP) caused an inhibition of the thymidylate synthetase activity of Walker rat mammary carcinoma cells in tissue culture, which could be reversed by concomitant treatment with N2,O2' dibutyryl guanosine 3',5' monophosphate (dbcGMP). There was no effect on thymidine kinase activity. The DNA polymerase activity of whole cells, but not broken-cell preparations was markedly inhibited by a dose of mbcAMP (100 micrograms/ml) having little effect on growth rate. This inhibition could be reversed to some extent by simultaneous treatment of the cells with caffeine. Treatment with mbcAMP produced a decrease in the level of dTTP and a concomitant rise in the levels of dATP, dGTP and dCTP. This situation was reversed in combination with dbcGMP, with levels of the deoxyribonucleoside triphosphates tending to revert back to control values. The effect of mbcAMP on thymidylate synthetase and DNA polymerase may account for its growth inhibitory effect.
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PMID:The effect of cyclic nucleotides on DNA polymerase, thymidylate synthetase, thymidine kinase and deoxynucleoside levels of Waler carcinoma. 718 96

We examined the effects of a combination of adriamycin (ADR) and caffeine on DNA and protein biosynthesis and on the activities of DNA polymerase alpha and beta in normal and tumor tissue. The decrease in DNA and protein biosynthesis in tumor produced by caffeine combined with ADR were 2.5 and 2.4 times greater, respectively, compared with ADR alone. The combination of caffeine and ADR enhanced the decrease in DNA polymerases activities in the tumor which was induced by ADR, the decreases being 1.8 and 1.6 times greater, respectively, than that of ADR alone. In contrast, these ADR-induced changes in normal tissues were not enhanced by the combination with caffeine. The combination with caffeine had no effect on ADR concentration in normal tissues, but in the tumor, it increased the ADR concentration to 2.1 times that of ADR alone. In vitro, ADR efflux from Ehrlich ascites carcinoma cells was significantly inhibited by exposure to caffeine. These findings indicate that the effect of caffeine on ADR concentration in the cell plays an important role in the mechanism by which caffeine enhances ADR antitumor activity.
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PMID:Mechanism of caffeine modulation of the antitumor activity of adriamycin. 786 36

This article presents the identification and characterization of the PAK1 gene of Saccharomyces cerevisiae, and the biochemical characterization of the protein kinase activity that it encodes. Overexpression of the PAK1 gene product suppresses temperature-sensitive mutations of the poll (cdc 17) gene, which encodes DNA polymerase alpha. Overexpression and suppression can be achieved either by expressing PAK1 from a high-copy-number plasmid, or by GAL1-induced transcription of PAK1. Gene disruption of PAK1 indicates that it is not an essential gene. The PAK1 gene encodes a protein with a kinase consensus domain. By deletion analysis and site-directed mutagenesis, we demonstrate that the complete and active kinase consensus domain is required for suppression. A glutathione-S-transferase (GST)-Pak1 fusion protein, overproduced in bacteria, can be purified in an active form with glutathione affinity beads or by immunoprecipitation. Thus, other protein subunits of Pak1 are not required for its activity. In vitro protein kinase assays show that GST-Pak1 can autophosphorylate, and can phosphorylate casein as an exogenous substrate. The phenotype of the suppressed cdc17-1 cells indicates that Pak1 suppression is inefficient and does not restore the wild-type phenotype. Pak1 suppression requires Rad9 function, but Pak1 does not affect Rad9 function. Overexpression of PAK1 does not enhance the expression of the POL1 gene. Pak1 may function by modifying and partially stabilizing thermolabile DNA polymerases, perhaps during DNA repair, because pak1 mutant cells are caffeine sensitive.
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PMID:Overexpression of the protein kinase Pak1 suppresses yeast DNA polymerase mutations. 934 78


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