Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

5-AZA-2'-deoxycytidine-5'-monophosphate (5-AZA-dCMP) was tested as a substrate, and 5-aza-2'-deoxycytidine-5'-triphosphate (5-AZA-dCTP) was tested as an allosteric effector of purified spleen dCMP deaminase. Graphic analysis of the velocity of deamination of 5-AZA-dCMP versus its concentration gave a hyperbolic curve in which the estimated apparent Km was 0.1 mM. Since this curve was not sigmoidal and 5-AZA-dCMP at low concentrations stimulated the rate of deamination of the natural substrate, dCMP, it was proposed that the binding of 5-AZA-dCMP to the allosteric enzyme dCMP deaminase induced the R form. At substrate saturation, the rate of deamination of dCMP was 100-fold greater than that of 5-AZA-dCMP. dTTP inhibited the deamination of 5-AZA-dCMP with first-order kinetics. This inhibition was reversed by either 5-AZA-dCTP or dCTP. However, dCTP alone produced only a weak activation of the deamination of 5-AZA-dCMP in comparison to the potent activation when dCMP was the substrate. 5-AZA-dCTP was just as effective as dCTP for the allosteric activation of the deamination of dCMP. These results indicate that dCMP deaminase can play an important role in the metabolism 5-aza-2'-deoxycytidine nucleotides and may possibly modulate some of the pharmacological activity of this antimetabolite.
Mol Pharmacol 1984 May
PMID:Kinetic interaction of 5-AZA-2'-deoxycytidine-5'-monophosphate and its 5'-triphosphate with deoxycytidylate deaminase. 620 26

Misincorporation by avian myeloblastosis virus reverse transcriptase in the presence of a single deoxyribonucleoside triphosphate was studied using 32P-labeled DNA primers annealed to the appropriate template DNA, and polyacrylamide-urea gel electrophoresis to measure the extension of the primer chains. With most primer-template combinations, greater than 50% of the primers were extended by the addition of a single incorrect nucleotide onto the end of the primer chain. Unexpectedly, one primer-template combination was not extended in the presence of dCTP, although misincorporation occurred with the other deoxyribonucleoside triphosphates. In another case, terminal misincorporation of two rather than one dT residue was observed. The primer termini containing unpaired nucleotides were efficiently extended upon addition of the other three deoxyribonucleoside triphosphates, even in the case where the primer terminus contained two unpaired nucleotides. Misincorporation was confirmed by direct sequence analysis. These results indicate that the frequency of mutations following misincorporation by reverse transcriptase in the presence of a single deoxyribonucleoside triphosphate should be sufficiently high to allow detection of mutants by simple screening procedures. An analysis of the sequence of a mutant resulting from misincorporation at the M13mp2 AvaII site revealed that following introduction of the DNA into Escherichia coli cells, mismatch repair preceded replication.
J Mol Appl Genet 1984
PMID:Efficient misincorporation by avian myeloblastosis virus reverse transcriptase in the presence of a single deoxyribonucleoside triphosphate. 620 55

Human T leukemic lymphocytes are highly susceptible to growth inhibition by dAdo. We have investigated this phenomenon using analytical DNA flow cytometry. By using (a) bromodeoxyuridine quenching of Hoechst 33342 fluorescence and (b) the drug ICRF-159, a selective G2 - M-blocking agent, we show that dAdo causes a G1 block in cultured T leukemic cells and that cells in the S phase exposed to dAdo are able to complete that S phase, pass through G2 + M, and return to the G1 phase. Centrifugal elutriation was used to enrich cells for various phases of the cell cycles. dAdo caused elevation of the dATP pool to a similar extent in G1, S, and G2 - M-enriched cell fractions, but did not cause a fall in the dCTP pool. These findings indicate that dAdo induces a G1 block via elevation of dATP pools, apparently independently of inhibition of ribonucleotide reductase.
Mol Pharmacol 1984 Sep
PMID:Analytical DNA flow cytometric analysis of deoxyadenosine toxicity in cultured human leukemic lymphoblasts. 633 78

An aphidicolin-resistant ( aphr ) mutant of Chinese hamster V79 cells, aphr -4-2, is shown to be slow-growing, sensitive to ultraviolet (UV) irradiation, hypermutable for spontaneous and UV-induced mutations, and known to contain an aphr mutant DNA polymerase-alpha, with a 10-fold reduction in the Km for dCTP but not for dATP. We show here that the mutant had a normal repair replication measured by unscheduled DNA synthesis assay. The mutant was specifically sensitive and hypermutable to UV and N-methyl-N'-nitro-N-nitrosoguanidine, but it had normal sensitivity to ionizing radiation and dimethyl sulfate. Unlike the V79 (wt) cells, the mutant exhibited further enhancement in the already elevated mutability following UV and conditioned medium treatment. The mutant characteristic is explained by the presence of an error-prone long-patch excision repair synthesis. The association in the mutant properties--an aphr DNA polymerase-alpha, UV sensitivity, and hypermutability to UV-induced mutation--provides the genetic evidence that DNA polymerase-alpha is likely to be involved in UV-induced DNA repair synthesis.
Somat Cell Mol Genet 1984 May
PMID:Evidence for mutagenic repair in V79 cell mutant with aphidicolin-resistant DNA polymerase-alpha. 642 68

Escherichia coli DNA polymerase I (Klenow fragment), DNA polymerase alpha from both calf thymus and human lymphoma cells and DNA polymerase beta from calf thymus and Novikoff hepatoma cells can incorporate nucleotides opposite N-guanin-8-yl-acetyl-2-aminofluorene in DNA. The polymerases incorporate dCTP opposite some AAF-dG lesions when Mg2+ is the divalent cation. Substitution of Mn2+ for Mg2+ broadens the specificity of insertion: E. coli DNA polymerase I (Klenow fragment) also inserts A, and at specific sites G or T; DNA polymerase alpha inserts any of the four dNTPs with A and C incorporated preferentially to G and T. Polymerase beta is specific, inserting mainly C even in the presence of Mn2+. The Km for addition of dATP opposite a lesion by E. coli polymerase I (Klenow fragment) in the presence of Mn2+ is about 0.5 mM. dNMPs increase the insertion of nucleotides opposite AAF-dG in the presence of Mg2+ and increase both the rate and number of sites at which incorporation occurs in the presence of Mn2+. dNTP alpha S and recA protein increase only the insertion of C. We suppose that the incorporation of dCTP reflects normal base-pairing with the AAF-deoxyguanine in the anti conformation, whereas insertion of the other nucleotides (including some of the C) reflects insertion opposite the AAF adduct in its preferred syn conformation. The fact that the DNA polymerase plays a role in determining the specificity of insertion opposite a lesion terminating DNA synthesis suggests that the spectrum of base substitution mutagenesis seen in vivo may reflect the properties of the protein components, including the polymerase, involved in bypass synthesis.
J Mol Biol 1984 Sep 25
PMID:A role for DNA polymerase in the specificity of nucleotide incorporation opposite N-acetyl-2-aminofluorene adducts. 649 59

Deoxycytidylate deaminase has been highly purified (1232-fold) from human leukemia CCRF-CEM cells. The native molecular weight of the enzyme is 108 000 and subunit molecular weight 50 500, suggesting that the native enzyme exists as a dimer. The enzyme exhibits a sigmoidal initial velocity vs substrate concentration curve and is regulated by allosteric effectors, dCTP and TTP. The curve relating substrate concentration to initial velocity was changed from a sigmoidal shape to a hyperbolic one by the activator dCTP, while the inhibitor TTP increased the sigmoidicity of the curve. The molecular weight of deoxycytidylate deaminase was unchanged in the presence of allosteric effectors, indicating that aggregation-disaggregation is not the basis of regulation. Deoxycytidylate deaminase exhibited the greatest affinity for the substrate dCMP, with lesser affinity for ara-CMP, and least affinity for CMP. Ara-CMP was an effective substrate in the presence of dCTP concentrations exceeding 4 microM. These data indicate that human neoplastic cell deoxycytidylate deaminase is a highly regulated allosteric enzyme, which is likely to have a significant influence on cellular dUMP, dCTP and TTP pools. These findings further suggest, that the enzyme through its influence on dUMP levels is likely to modulate the biochemical effects of pyrimidine antimetabolites active against the thymidylate synthetase reaction and in the presence of elevated dCTP pools will promote deamination of ara-CMP to the inactive ara-UMP.
Mol Cell Biochem 1983
PMID:Kinetic behaviour and allosteric regulation of human deoxycytidylate deaminase derived from leukemic cells. 658 81

The effects of methotrexate (MTX) in the presence or absence of exogenous thymidine (dThd, 10(-5) M) or hypoxanthine (Hx, 10(-4) M) on cell cycle kinetics and deoxyribonucleoside triphosphate pools (dNTP) were studied in cultured human leukemic T-cells (CCRF-CEM). MTX cytotoxicity was found to increase linearly with drug dose for MTX concentrations between 10(-9) M and 10(-7) M. No further increase in cytoxicity was observed with much higher MTX concentrations (10(-7) M-10(-4) M). A similar dose-response relationship was found for both MTX-induced inhibition of DNA synthesis and changes in dTTP and dGTP pools but not for either MTX-induced inhibition of purine synthesis or changes in dATP and dCTP pools. Exogenous dThd reduced MTX cytotoxicity, at all MTX concentrations examined, but Hx reduced cytotoxicity only at MTX concentrations less than 6 X 10(-8) M and potentiated toxicity with higher MTX concentrations. This potentiation of cytotoxicity was accompanied by substantial elevation of dATP pools. In all instances where dThd or Hx reduced MTX cytotoxicity, a concomitant increase in both dTTP and dGTP levels and in the rate of DNA synthesis was observed. These results suggest a close correlation between MTX-induced alterations of dNTP and inhibition of DNA synthesis and subsequent MTX cytotoxicity. The possible modulation of MTX cytotoxicity by purines is discussed.
Mol Pharmacol 1982 Jan
PMID:Biochemical and cell cycle perturbations in methotrexate-treated cells. 698 94

We investigated the mechanism of action of 2-aminopurine (Apur) in eucaryotic cells. By analogy with studies in procaryotic systems, the base analog is presumed to incorporate into DNA predominantly opposite T where, upon subsequent DNA replication, it can mispair with C, inducing an A:T leads to G:C transition. This model predicts that Apur-induced mutagenesis will be enhanced by factors that favor formation of Apur-C mispairs, e.g., high levels of dCTP or low levels of TTP. We describe the use of a mutant T-lymphosarcoma cell line, AraC-6-1, which has an abnormally high dCTP pool and a low TTP pool, to test this prediction. AraC-6-1 cells were three- to fivefold more mutable by Apur than their parental cell line, NSU-1. This enhanced mutability by Apur could not be explained by altered incorporation of 3H-labeled Apur, by generally impaired ability to repair DNA damage, or by a direct effect of Apur on the endogenous deoxynucleotide pools. The addition of 10 microM thymidine to the growth medium of AraC-6-1 cells lowered their high dCTP pool (two- to threefold), raised the TTP pool (two- to threefold), and abolished their enhanced mutability by Apur. Further manipulation to produce an abnormally high TTP/dCTP ratio suppressed Apur-induced mutagenesis (8- to 10-fold) in both AraC-6-1 and NSU-1 cells. These observations support the hypothesis that Apur induces A:T leads to G:C transitions in mammalian cells by a mispairing mechanism.
Mol Cell Biol 1982 Sep
PMID:Mechanism of 2-aminopurine mutagenesis in mouse T-lymphosarcoma cells. 698 47

Three fractions of nascent DNA labeled with [3H]dCTP in isolated nuclei of Misgurnus fossilis embryos were observed after sedimentation in alkaline sucrose: 1) high-molecular-weight DNA strands larger than 3000 nucleotides; 2) fragments of DNA with average length about 200 nucleotides; 3) low-molecular-weight DNA fragments shorter than 100 nucleotides. The labeled DNA was accumulated in the high-molecular-weight fraction (1) with an increase of incubation time. This process indicated the sealing of Okazaki fragments to parental DNA in the course of DNA replication. Adenosine diphosphate stimulated the label accumulation in larger DNA fragments. Embryo nuclei contain Ca-dependent desoxyribonuclease which can digest both exogenous and endogenous DNA DNase I treatment of nuclei dramatically stimulated the label incorporation into nuclear DNA.
Mol Biol (Mosk)
PMID:[DNA synthesis in isolated nuclei of Misgurnus fossilis loach embryos. II. Sedimentation of newly-formed DNA in an alkaline sucrose concentration gradient. Effect of calcium ions]. 744 70

Human diploid fibroblasts, strain MRC-5, were permeabilized by electroporation and treated with 5-methyl deoxycytidine triphosphate (5-methyl dCTP) in the S phase of the cell cycle. The frequency of TGR HPRT- cells was increased up to 20-fold in comparison to control untreated cultures. Representative TGR clones were unable to grow in HAT, and these were treated with 5-azacytidine (5-aza-CR). In many cases subsequent growth in HAT medium was observed, but in others it is likely that the cells had run out of growth potential. The results provide the first evidence of the silencing and reactivation of a gene in normal diploid mammalian cells.
Somat Cell Mol Genet 1995 May
PMID:Evidence for gene silencing by DNA methylation in normal human diploid fibroblasts. 748 35


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