Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.7 (DNA polymerase)
 17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A triple (aphr ara-Ar and araCr) mutant (AP7) of Chinese hamster ovary cells resistant to DNA polymerase inhibitors is described. The aphidicolin-resistance of the mutant was stable and inherited as a dominant genetic trait. The DNA polymerase alpha from the wild type (aphs) and the mutant (aphr) cells differed in their elution profiles on DEAE-cellulose chromatography and in their molecular weights which were 192,000 for the wild type (CHO-K-1, AC6a) and 165,000 for the mutant (AP7) enzymes.
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PMID:A Chinese hamster ovary cell mutant resistant to aphidicolin. 392 33

Synergistic cell killing of human lymphoblastic leukemia cell line, CCRF-CEM, occurred when hydroxyurea (HU) was administered before 1-beta-D-arabinofuranosylcytosine (ara-C). At the optimal dose of HU (1mM), the ara-CTP concentration increased 4-fold and the intracellular accumulation of ara-C increased 4-fold, while the dCTP concentration decreased by more than 50%. Increased intracellular accumulation of ara-C after HU treatment was also observed in human acute myelogenous leukemic cells in circulating blood. Therefore, the synergistic cell kill of HU and ara-C may be the consequence of greater inhibition of DNA polymerase by the increased level of ara-CTP in the presence of the decreased concentration of the natural substrate of this enzyme, dCTP. This synergism was not due to an increased incorporation of ara-C into DNA since the treatment of cells with HU did not enhance the ara-C incorporation into DNA but rather suppressed it.
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PMID:Mechanism of synergistic cell killing by hydroxyurea and cytosine arabinoside. 393 Apr 50

Genetic characterizations of the Chinese hamster ovary cell mutants resistant to the DNA polymerase inhibitors (aphidicolin, ara-A and ara-C) have been described. Resistance to all three inhibitors showed dominance among the progeny of somatic cell crosses between the wild type and mutant parents. Analysis of the segregation of the drug-resistant character among 566 hybrid progeny from somatic crosses between the wild type (aphs, ara-As, and ara-Cs) and the triple mutants (aphr, ara-Ar, ara-Cr) showed the involvement of at least three unlinked genes in controlling the expression of the resistance to different DNA polymerase inhibitors. The mutant (aphr) DNA was used to transfect aphidicolin resistance to recipient mouse Ltk- cells either directly or in combination with the plasmid pTK2 DNA. The aphidicolin resistance of the transfected cells was found to be a stable phenotype and could be used in multiple rounds of transfection, indicating the chromosomal integration of the transfecting gene.
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PMID:Chinese hamster ovary cell mutants resistant to DNA polymerase inhibitors. II. Segregational analysis and DNA transfection of the aphr gene. 393 Sep 22

Isolation and characterization of Chinese hamster ovary cell mutants resistant to different DNA polymerase inhibitors (aphidicolin, ara-A and ara-C) have been described. A particular mutant (JK3-1-2A) characterized in detail was found to grow and synthesize DNA in medium containing an amount of aphidicolin tenfold greater than that which completely inhibited the growth and the DNA synthesis of the wild-type cells. An almost twofold increase in the specific activity of the DNA polymerase alpha was seen in this mutant. The mutant DNA polymerase showed altered aphidicolin inhibition kinetics of dCMP incorporation; the apparent Km for dCTP and the apparent Ki for aphidicolin were increased in the mutant. These alterations in the kinetic parameters were, however, abolished upon further purification of the enzyme. Ara-CTP was found to act as a competitive inhibitor of the dCMP incorporation by both the wild type and mutant enzymes. In contrast, the effect of aphidicolin on dCMP incorporation was either competitive (wild-type enzymes) or noncompetitive (mutant enzyme). The data presented showed that the sites of action for aphidicolin and ara-CTP were distinct; likewise the dCTP binding site appeared to be separate from other dNTP(s) binding sites. The drug resistance of the mutant was inherited as a dominant trait.
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PMID:Chinese hamster ovary cell mutants resistant to DNA polymerase inhibitors. I. Isolation and biochemical genetic characterization. 393 Sep 21

The mechanism of inhibition of DNA synthesis by 1-beta-D-arabinofuranosyl-ATP (ara-ATP) and the potentiation of this inhibition by 6-mercaptopurine ribonucleoside 5'-monophosphate (6-MPR-P) have been investigated with mammalian DNA polymerase delty by using poly(dA-dT) as the template. The inhibition of DNA synthesis by ara-ATP correlates with incorporation of ara-AMP into poly(dA-dT). Nearest-neighbor analysis indicates that ara-AMP does not act as an absolute chain terminator but rather that chains with 3'-terminal arabinosyl nucleotides are extended slowly. The inhibition of DNA synthesis by ara-ATP is markedly enhanced by the addition of the nucleotide derivative of 6-mercaptopurine, 6-mercaptopurine ribonucleoside 5'-monophosphate. The increased inhibition of DNA synthesis in the presence of 6-MPR-P is due to increased incorporation of ara-AMP. The mechanism by which 6-MPR-P increases the incorporation of ara-AMP is by selective inhibition of the 3' to 5' exonuclease activity of DNA polymerase, thereby preventing the removal of newly incorporated ara-AMP at 3' termini of DNA chains.
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PMID:Mechanism of inhibition of deoxyribonucleic acid synthesis by 1-beta-D-arabinofuranosyladenosine triphosphate and its potentiation by 6-mercaptopurine ribonucleoside 5'-monophosphate. 615 66

9-beta-D-Arabinofuranosyladenine (ara-A), 1-beta-D-arabinofuranosylcytosine (ara-C), and their 5'-triphosphates (ara-ATP and ara-CTP) were tested for ability to inhibit the hepatitis B virus (HBV)-associated deoxyribonucleic acid (DNA) polymerase. Ara-C did not inhibit the HBV DNA polymerase at the concentrations tested, ara-A did so by 50% at a concentration of 30 mM, with the inhibition noncompetitive with respect to deoxyadenosine 5-triphosphate (dATP). Ara-ATP and ara-CTP inhibited the DNA polymerase test competitively with respect to dATP and dCTP, respectively. Both compounds were also active after initiation of the DNA polymerase reaction. The inhibition caused by ara-ATP and ara-CTP was shown to be reversible, with no evidence that ara-ATP or ara-CTP was incorporated into the HBV DNA.
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PMID:Inhibition of hepatitis B virus deoxyribonucleic acid polymerase by the 5'-triphosphates of 9-beta-D-arabinofuranosyladenine and 1-beta-D-arabinofuranosylcytosine. 616 46

The modulating effect of hydroxyurea (HU) on 1-beta-D-arabinofuranosylcytosine (ara-C) metabolism and cytotoxicity was evaluated in L1210 cells and the human promyelocytic leukemic cells HL-60. A dose- and time-dependent HU exposure was observed which resulted in maximum deoxycytidine 5'-triphosphate reduction, intracellular ara-C accumulation, 1-beta-D-arabinofuranosylcytosine 5'-triphosphate formation, and cytotoxicity as determined by soft agar cloning. For the L1210 cells, a 5-hr pretreatment of 5 mM HU was optimum. The best result obtained with the HL-60 cells was after a 24-hr exposure of 1 mM HU. There was also a maximum incorporation of ara-C into DNA in both cells following these optimal pretreatment conditions. Cytofluorometric analysis demonstrated that this HU treatment resulted in a maximum accumulation of L1210 and HL-60 cells in the pre-S phase of the cell cycle and that after removal of the HU there was a rapid progression of the cell population through S phase. Because cytotoxicity of ara-C is considered to be predominantly from the inhibition of DNA polymerase and/or the incorporation into DNA, the cytokinetic and biochemical modulatory effects of HU must both be contributing factors to consider in achieving maximal cell kill from this drug sequence.
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PMID:Biochemical and cytokinetic modulation of L1210 and HL-60 cells by hydroxyurea and effect on 1-beta-D-arabinofuranosylcytosine metabolism and cytotoxicity. 618 85

Ara-C should be converted to ara-CTP to inhibit DNA polymerase in the malignant cells but is rapidly inactivated to uracil arabinoside (ara-U) by cytidine deaminase in human tissue. Therefore, production as well as maintenance of ara-CTP in the cells is a function of both phosphorylation and deamination of ara-C, but is more dependent on the latter, because the deamination is several times superior to the former in terms of enzymatic activities. In chemotherapy with ara-C, the rate of the inactivation should be estimated for evaluating antitumor effect of the agent. Determination of serum or plasma deaminase activity can be a useful parameter of the inactivation. Attempts have been made to enhance the antitumor activity of ara-C by preventing deamination and a number of ara-C derivatives resistant to the deamination such as cyclocytidine, ara-C-5'-ester and acyl ara-C have been introduced. Cyclo-C gradually receives non-enzymatic hydrolysis to produce ara-C in neutral medium, which is useful for maintaining plasma ara-C level. Acyl ara-C such as behenoyl-ara-C (BHAC) is well incorporated into the cells and is highly distributed to lipophilic components such as membrane, microsome and mitochondria in the cells. The extremely gradual conversion of BHAC to ara-C in the cells is considered to be useful for maintaining effective intracellular concentration. A part of BHAC could be phosphorylated before deacylation. After intravenous administration of BHAC, the plasma drug concentrations are maintained significantly longer than those after the administration of the equivalent dose of ara-C. Therefore, BHAC is more resistant to the deamination than cyclo-C and the antitumor effect of the former is suspected to be milder but prolonged than that of ara-C or cyclo-C.
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PMID:[Chemotherapy of the malignancies from the viewpoint of pharmacology and biochemistry of cytosine arabinoside (ara-C) and its derivatives]. 619 11

The severity of herpetic keratitis induced by 9-(2-hydroxyethoxymethyl) guanine-resistant strains of herpes simplex virus was significantly reduced by cotherapy with 9-beta-D-arabinofuranosyladenine (ara-A) and 2-deoxycoformycin. Therapy with 5-trifluoromethyl-2'-deoxyuridine (F3TdR) significantly reduced the severity of keratitis induced by an acyclovir-resistant strain with a defective DNA polymerase. Therapy with 3 percent acyclovir ointment slightly reduced the number of herpetic lesions produced by either deoxypyrimidine kinase or DNA polymerase defective viruses, despite these viruses being 100 to 1000 times more resistant to acyclovir than the wildtype strain. Therapy with 3 percent ara-A ointment alone significantly reduced the severity of lesions produced by the wildtype herpes strain. Therapy with ara-A alone did not reduce the severity of disease induced by any of the acyclovir-resistant mutants. The sensitivity of the wildtype and mutant viruses to nucleoside analogs was confirmed by yield-reduction assays conducted with Vero cells. These studies indicate that cotherapy with ara-A and an adenosine deaminase inhibitor was a reasonable alternative therapy for keratitis due to mutants resistant to therapy with nucleoside analogs which require the virus-specified deoxypyrimidine kinase or DNA polymerase, while ara-A alone was not an effective alternative.
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PMID:Chemotherapy of herpetic keratitis induced by acyclovir-resistant strains of herpes simplex virus type 1. 628 20

The physical map limits of DNA sequences within the DNA polymerase locus of herpes simplex virus (HSV) type 1 that define resistance mutations to adenine arabinoside (ara-A) and E-5-(2-bromovinyl)-2'-deoxyuridine (BVDU) were determined. Intertypic recombinants between HSV types 1 and 2, generated by marker rescue of temperature-sensitive mutations, had genome structures determined by restriction endonuclease analysis and were used to show that the resistance mutation for ara-Ar-1 is closely linked to the resistance mutations for phosphonoacetic acid (paar-1) and acycloguanosine (acvr-1) within a region of 2.6 kilobase pairs (kbp) in the HSV DNA polymerase locus. The resistance mutation for bvdur-1 is defined by a 2.9-kbp region that overlaps with the region defining resistance to the other three drugs but that is transferred separately. The DNA polymerase locus also contains a 2.2-kbp region that maps adjacent to and to the left of the region defining the bvdur-1 mutation which can be transferred separately and defines a region determining the HSV-1-specific sensitivity to BVDU in a manner analogous to that to acyclovir.
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PMID:Resistance of herpes simplex virus to adenine arabinoside and E-5-(2-bromovinyl)-2'-deoxyuridine: a physical analysis. 628 86


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