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)

3'-Fluoro-2',3'-dideoxythymidine 5'-(alpha-methylphosphonyl)-beta,gamma- diphosphate and 2'-deoxythymidine-5'-(alpha-methylphosphonyl)-beta, gamma- diphosphate have been synthesized. Both compounds are incorporated into DNA chains during catalysis by reverse transcriptases of human immunodeficiency (HIV) and avian myeloblastosis (AMV) viruses, DNA polymerase beta from rat liver, terminal deoxynucleotidyl transferase from calf thymus and (at a very low rate) is by E. coli DNA polymerase I, Klenow fragment. The first compound is a termination substrate while the second is capable of multiple incorporation into the DNA chains. For instance, reverse transcriptase catalysis resulted in the appearance of 8 residues of second compound. DNA polymerases alpha and epsilon from human placenta incorporated none of the above compounds into DNA chains, although an inhibition of DNA synthesis by both compounds was observed with all enzymes mentioned. The 3'----5'-exonuclease activity of DNA polymerase I, Klenow fragment, hydrolyzed DNA fragments containing phosphonomethyl internucleoside groups, while such DNA fragments were resistant to the E. coli exonuclease III.
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PMID:Formation of phosphonester bonds catalyzed by DNA polymerase. 137 65

(-)-2'-Deoxy-3'-thiacytidine (3TC) is a selective inhibitor of human immunodeficiency virus replication in vitro (J. A. V. Coates, N. Cammack, H. J. Jenkinson, A. J. Jowett, M. I. Jowett, B. A. Pearson, C. R. Penn, P. L. Rouse, K. C. Viner, and J. M. Cameron, Antimicrob. Agents Chemother. 36:733-739, 1992). The effect of 3TC 5'-triphosphate on both the RNA-dependent and DNA-dependent activities of human immunodeficiency virus type 1 reverse transcriptase and DNA polymerases alpha, beta, and gamma from HeLa cells was investigated. 3TC 5'-triphosphate is a competitive inhibitor (with respect to dCTP) of the RNA-dependent DNA polymerase activity (apparent Ki = 10.6 +/- 1.0 to 1.24 +/- 5.1 microM, depending on the template and primer used); the DNA-dependent DNA polymerase activity is 50% inhibited by a 3TC 5'-triphosphate concentration of 23.4 +/- 2.5 microM when dCTP is present at a concentration equal to its Km value. Chain elongation studies show that 3TC 5'-triphosphate is incorporated into newly synthesized DNA and that transcription is terminated in a manner identical to that found for ddCTP. The 50% inhibitory concentrations of 3TC 5'-triphosphate against DNA polymerases alpha, beta, and gamma at concentrations of dCTP equal to the Km were 175 +/- 31, 24.8 +/- 10.9, and 43.8 +/- 16.4 microM, respectively. More detailed kinetic studies with 3TC 5'-triphosphate and DNA polymerases beta and gamma are consistent with the fact that inhibition of these enzymes by 3TC 5'-triphosphate is competitive with respect to dCTP. The values of Ki were determined to be 18.7 microM for DNA polymerase beta and 15.8 +/- 0.8 microM for DNA polymerase gamma.
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PMID:Effects of (-)-2'-deoxy-3'-thiacytidine (3TC) 5'-triphosphate on human immunodeficiency virus reverse transcriptase and mammalian DNA polymerases alpha, beta, and gamma. 138 25

In order to clarify the biological activities of (-)-oxetanocin G, and (-)-oxetanocin A and its carbocyclic analogue, (-)-carboxetanocin G, the inhibitory effects of triphosphate derivatives of these compounds (OXT-GTP, OXT-ATP, and C-OXT-GTP) on eukaryotic and viral DNA polymerases were examined. DNA polymerase alpha purified from calf thymus was weakly inhibited by OXT-GTP and OXT-ATP but strongly by C-OXT-GTP, the Ki value being 0.22 microM. On the other hand, rat DNA polymerase beta was not affected by these analogues. DNA polymerase gamma purified from bovine testes was very weakly inhibited by OXT-GTP and OXT-ATP, but not by C-OXT-GTP. DNA polymerase from herpes simplex virus type-II (HSV-II) was strongly inhibited by all three analogues, the Ki values ranging from 0.5 to 1.0 microM. Human immunodeficiency virus-encoded reverse transcriptase (HIV RT) was also strongly inhibited by these three analogues, the Ki value of C-OXT-GTP being slightly smaller than that of OXT-GTP or OXT-ATP. Analysis of products synthesized on singly primed M13 single-stranded DNA by DNA polymerase alpha, HSV-II DNA polymerase or HIV RT in the presence of the analogues revealed that OXT-GTP and C-OXT-GTP were incorporated into DNA and caused chain termination mainly at sites one or two nucleotides beyond the cytosine bases on the template.
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PMID:Inhibitory effects of triphosphate derivatives of oxetanocin G and related compounds on eukaryotic and viral DNA polymerases and human immunodeficiency virus reverse transcriptase. 138 92

We have studied the expression pattern of DNA polymerase beta in two different models of in vivo cell proliferation. Both mRNA levels and enzyme activity of DNA polymerase beta markedly increased before and/or during DNA synthesis in proliferating hepatocytes in mitogen-treated and partially hepatectomized rats. The time-courses of the expression of the gene coding for DNA polymerase beta were significantly different in the two cell systems. A 5-fold increase in DNA polymerase beta mRNA was observed 8 h after lead nitrate administration, i.e. well before the onset of DNA synthesis. In the regenerative liver cells a 3-fold increase in the amount of mRNA was observed 24-48 h after partial hepatectomy, the event being coincident with extensive DNA synthesis. In both systems, the increase of mRNA levels was always paralleled by an increase in enzyme activity, suggesting that DNA polymerase beta activity may be regulated at a pre-translational level.
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PMID:Involvement of DNA polymerase beta in proliferation of rat liver induced by lead nitrate or partial hepatectomy. 139 62

In Salmonella typhimurium, dnaQ null mutants (encoding the epsilon editing subunit of DNA polymerase III [Pol III]) exhibit a severe growth defect when the genetic background is otherwise wild type. Suppression of the growth defect requires both a mutation affecting the alpha (polymerase) subunit of DNA polymerase III and adequate levels of DNA polymerase I. In the present paper, we report on studies that clarify the nature of the physiological defect imposed by the loss of epsilon and the mechanism of its suppression. Unsuppressed dnaQ mutants exhibited chronic SOS induction, indicating exposure of single-stranded DNA in vivo, most likely as gaps in double-stranded DNA. Suppression of the growth defect was associated with suppression of SOS induction. Thus, Pol I and the mutant Pol III combined to reduce the formation of single-stranded DNA or accelerate its maturation to double-stranded DNA. Studies with mutants in major DNA repair pathways supported the view that the defect in DNA metabolism in dnaQ mutants was at the level of DNA replication rather than of repair. The requirement for Pol I was satisfied by alleles of the gene for Pol I encoding polymerase activity or by rat DNA polymerase beta (which exhibits polymerase activity only). Consequently, normal growth is restored to dnaQ mutants when sufficient polymerase activity is provided and this compensatory polymerase activity can function independently of Pol III. The high level of Pol I polymerase activity may be required to satisfy the increased demand for residual DNA synthesis at regions of single-stranded DNA generated by epsilon-minus pol III. The emphasis on adequate polymerase activity in dnaQ mutants is also observed in the purified alpha subunit containing the suppressor mutation, which exhibits a modestly elevated intrinsic polymerase activity relative to that of wild-type alpha.
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PMID:DNA replication defect in Salmonella typhimurium mutants lacking the editing (epsilon) subunit of DNA polymerase III. 140 Feb 46

A specific inhibitor of DNA polymerase alpha was isolated from the lipid fraction prepared from myxoamoebae of a true slime mold, Physarum polycephalum. The purified substance was subjected to structural studies by fast atom bombardment mass spectroscopy, infrared spectroscopy, and two-dimensional nuclear magnetic resonance spectroscopy. The structure of this substance was thereby suggested to be a novel lysophosphatidic acid (LPA) composed of cyclic phosphate and cyclopropane-containing hexadecanoic acid. Then we named this substance PHYLPA (Physarum LPA). PHYLPA inhibited more than 80% of the affinity-purified calf thymus DNA polymerase alpha activity at a concentration of 10 micrograms/ml (approximately 20 microM). Inhibition was observed for DNA polymerase alpha but not for DNA polymerase beta or gamma from various eukaryotic species, nor did it inhibit DNA polymerase I from E. coli. From kinetic analyses, the inhibition was considered to be caused by the interaction of PHYLPA with the template DNA.
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PMID:Inhibition of eukaryotic DNA polymerase alpha with a novel lysophosphatidic acid (PHYLPA) isolated from myxoamoebae of Physarum polycephalum. 140 Apr 63

Although human DNA polymerase beta (DNA pol beta) shows 96% identity with rat DNA pol beta at the amino acid level, it is weakly expressed in Escherichia (E.) coli relative to the rat enzyme. The mechanism of this suppression was investigated. Pulse-chase protein labeling and steady state mRNA analysis showed that mature human DNA pol beta protein is relatively stable in E. coli and the levels of human and rat DNA pol beta mRNA were comparable indicating that the human DNA pol beta expression is suppressed at the translational level. By systematic expression analysis of a number of chimeric genes composed of human and rat cDNAs, two strong translational suppression regions were mapped in the human DNA pol beta mRNA; one was named TSR-1, corresponding to CGG encoding arginine (arg) at position 4 and the other, termed TSR-2, is located between codons 153 and 199. Since substitution of the rat Arg-4 codon with synonymous codons showed strong effects upon the expression level, we propose that the arg codon at the N-terminal coding region plays a role in modulating expression.
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PMID:Two regions in human DNA polymerase beta mRNA suppress translation in Escherichia coli. 140 1

The 39-kDa DNA polymerase beta (beta-Pol) molecule can be readily converted into two constituent domains by mild proteolysis; these domains are represented in an 8-kDa N-terminal fragment and a 31-kDa C-terminal fragment [Kumar et al. (1990a) J. Biol. Chem. 265, 2124-2131]. Intact beta-Pol is a sequence-nonspecific nucleic acid-interactive protein that binds both double-stranded (ds) and single-stranded (ss) polynucleotides. These two activities appear to be contributed by separate portions of the enzyme, since the 31-kDa domain binds ds DNA but not ss DNA, and conversely, the 8-kDa domain binds ss DNA but not ds DNA [Casas-Finet et al. (1991) J. Biol. Chem. 266, 19618-19625]. Truncation of the 31-kDa domain at the N-terminus with chymotrypsin, to produce a 27-kDa fragment (residues 140-334), eliminated all DNA-binding activity. This suggested that the ds DNA-binding capacity of the 31-kDa domain may be carried in the N-terminal segment of the 31-kDa domain. We used CNBr to prepare a 16-kDa fragment (residues 18-154) that spans the ss DNA-binding region of the 8-kDa domain along with the N-terminal portion of the 31-kDa domain. The purified 16-kDa fragment was found to have both ss and ds polynucleotide-binding capacity. Thermodynamic binding properties for these activities are similar to those of the intact enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Mammalian DNA polymerase beta: characterization of a 16-kDa transdomain fragment containing the nucleic acid-binding activities of the native enzyme. 142 Jan 47

DNA templates containing a modified base (O6-methylguanine, 8-hydroxyguanine, xanthine or hypoxanthine) which was located in nucleotide sequences corresponding to the 12th or 61st codon of a ras gene were synthesized and deoxynucleotide incorporation opposite the lesions was investigated. The templates were replicated by Taq DNA polymerase, recombinant rat DNA polymerase beta and mouse DNA polymerase alpha-primase complex. Sequence analysis of the replicated products indicated selective incorporation of nucleotide(s) opposite a modified base, depending on the kind of base and of DNA polymerase. This system is very useful to obtain results of in vitro replication of modified bases in ras sequences.
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PMID:In vitro replication study of modified bases in ras sequences. 146 11

The results presented here demonstrate that expression of a fos ribozyme limits Fos protein synthesis and enhances sensitivity of A2780DDP cells to antineoplastic agents, including cisplatin. Moreover, the reversal of this resistance is associated with down-regulation of dTMP synthase, DNA polymerase beta, topoisomerase I and hMTII-A, genes previously linked to DNA synthesis and repair. Thus these studies further implicate the role of the c-fos gene in DNA synthesis through modulation of expression of dTMP syntase, DNA polymerase beta and topoisomerase I. Finally, the use of ribozymes to circumvent drug resistance suggests their potential utility as agents to inhibit tumor cell growth.
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PMID:The utility of an anti-fos ribozyme in reversing cisplatin resistance in human carcinomas. 149 17


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