Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The inhibitors of DNA synthesis, 5-fluoro-2'-deoxyuridine and hydroxyurea, caused an inhibition of thymidine kinase, replicative DNA polymerase and CDP reductase activities in stimulated lymphocytes when they were exposed to the inhibitors during the early transformation period (0-17 hr). However, the enzyme activities were unaffected when the inhibitors were added to cells stimulated for more than 17 hr. As opposed to these enzymes the deoxycytidylate deaminase activity was unaffected by the inhibitors during the entire transformation period (0-28 hr). This indicates a close regulatory mechanism in lymphocytes between DNA synthesis and induction of enzymes involved in DNA replication. The inhibitory mechanism exerted by the inhibitors is for the moment unknown. It might be independent of the well-known inhibition of the target enzymes, thymidylate synthetase and ribonucleoside diphosphate reductase, since there was no immediate apparent correlation in time between depletion of the pool sizes and the inhibition of the enzyme activities.
...
PMID:Effect of 5-fluoro-2'-deoxyuridine and hydroxyurea on the phytohemagglutinin-induced increase of thymidine kinase, replicative DNA polymerase, deoxycytidylate deaminase and CDP reductase activities in human lymphocytes. 623 43

Activites of the enzymes DNA polymerase, thymidine kinase, thymidylate kinase, thymidylate synthase, and deoxycytidylate deaminase have been measured in rat and human normal and neoplastic liver, in human fetal liver, and in cell lines derived from human hepatomas and rat transplantable hepatomas. The activities of these enzymes were increased in rat transplantable hepatomas, relative to rat normal or host liver, to a degree corresponding to the rapid growth rate of these tumors. With the exception of thymidine kinase, which did not change, the activities of these enzymes increased in human hepatomas relative to the corresponding host liver (apparently normal liver tissue from the same patient) and to human normal liver. The increases in enzyme activity observed in human hepatomas were small in comparison with those found in the rapidly growing rat hepatomas. The activities of deoxycytidylate deaminase in both human and rat liver tissues were 2 to 3 orders of magnitude higher than those of the other enzymes assayed. Activities of the enzymes of DNA synthesis in a slow-growing cell line derived from a human hepatoma were similar to those in human hepatoma tissues. In the case of rapidly growing cell lines derived from rat and human hepatomas, enzyme activities were higher than those in the corresponding tissues.
...
PMID:Activities of some enzymes of pyrimidine and DNA synthesis in a rat transplantable hepatoma and human primary hepatomas, in cell lines derived from these tissues, and in human fetal liver. 624 89

A readily sedimentable nuclear fraction from Chinese hamster embryo fibroblast (CHEF/18) cells catalyzes incorporation of 14C-rCDP into DNA. Data indicated that this incorporation is made possible by the conversion of rCDP into a small and functionally compartmentalized, rather than a large and freely diffusible, pool of dCTP. This catalytically active sedimentable fraction from S phase CHEF/18 cells or actively replicating calf thymus cells contains nascent and template DNA, and numerous enzymes required for DNA biosynthesis including ribonucleoside diphosphate reductase, thymidylate synthetase, dihydrofolate reductase, DNA methylase, topoisomerase and DNA polymerase. We have named this catalytically active macromolecule the replitase. The replitase fraction contained spherical particles with a diameter of approximately 24 to 30 nm and had an estimated molecular weight on the order of 5 X 10(6).
...
PMID:Rapid incorporation of label from ribonucleoside disphosphates into DNA by a cell-free high molecular weight fraction from animal cell nuclei. 629 95

A multienzyme complex containing at least DNA polymerase (EC 2.7.7.7), thymidine kinase (EC 2.7.1.21), dTMP kinase (EC 2.7.4.9) nucleoside diphosphokinase (EC 2.7.4.6) and thymidylate synthetase was separated from the corresponding free enzymes of DNA precursor synthesis by gel filtration of a gently lysed preparation of HPB-ALL cells (a human lymphoblastoid cell line). The isolated incorporated the distal DNA precursors [3H]thymidine or [3H]dTMP into an added DNA template at rates comparable to those observed using the immediate precursor [3H]dTTP. Measurement of the apparent overall concentrations of [3H]dTTP produced during incorporation of [3H]thymidine and of [3H]dTMP were so low as to suggest that these precursors were channelled into DNA by the operation of a kinetically linked complex of precursor-synthesizing enzymes and of DNA polymerase. The DNA polymerase inhibitor 1-beta-D-arabinofuranosylcytosine triphosphate reduced incorporation of distal precursors into DNA. However [3H]dTTP did not accumulate in the reaction mixture. This suggested that the DNA polymerase regulated the flow of substrates through the complex. The results in this paper constitute direct evidence for the existence of multienzyme complexes of DNA synthesis in mammalian cells.
...
PMID:Gel filtration of a complex of DNA polymerase and DNA precursor-synthesizing enzymes from a human lymphoblastoid cell line. 630 81

We have previously shown that a fraction from the nuclei of S phase (DNA-synthesizing) Chinese hamster embryo fibroblasts (CHEF/18 cells) can be obtained that has a number of the enzyme activities required for DNA biosynthesis, and can catalyse the incorporation of labelled precursors into DNA (refs 1-4, also see ref. 8). This fraction, which we have termed the 'replitase', contains spherical particles of diameter approximately 25 nm, apparently multienzyme complexes for de novo DNA biosynthesis. Here we present evidence for the functional association of one of the enzyme activities, thymidylate synthase, with several of the other enzyme activities. Hydroxyurea, novobiocin and aphidicolin, inhibitors of ribonucleotide reductase, topoisomerase and DNA polymerase alpha, respectively, all inhibit thymidylate synthase in intact S phase CHEF/18 cells, but not in their soluble extracts. We suggest that these results reflect allosteric interactions between the subunits of a multienzyme DNA-synthesizing complex, which can be modulated by the specific inhibitors of individual enzyme activities in intact cells.
...
PMID:Inhibitor evidence for allosteric interaction in the replitase multienzyme complex. 640 86

Experiments were carried out to test for the presence of "channeling" in L1210 cells. L1210 cells were incubated in culture in the presence of labeled cytidine and "cold" deoxycytidine and conversely, in the presence of labeled deoxycytidine and "cold" cytidine. Cytidine did not inhibit the incorporation of [14C]deoxycytidine into DNA while deoxycytidine decreased the incorporation of [14C]cytidine into DNA. Further, in L1210 cells there was not a coordinate inhibition of thymidylate synthetase when either DNA polymerase was inhibited (aphidicolin) or ribonucleotide reductase was inhibited (hydroxyurea). These data indicate that leukemia L1210 cells do not selectively channel ribonucleotides to DNA through a tightly coupled enzyme complex.
...
PMID:Studies directed toward testing the "channeling" hypothesis--ribonucleotides----DNA in leukemia L1210 cells. 643 17

Thymidylate synthase-negative mutants of mouse FM3A cells were transformed to thymidine prototrophs by human DNA. The stable transformants had only human thymidylate synthase and segments of human DNA. They grew normally but had unusually high levels of the human enzyme. In two transformants examined, however, neither was the dTTP pool elevated nor the dCTP pool decreased. DNA synthesis in permeabilized cells of a transformant was more efficient than that in the wild type with dATP, dGTP, dCTP, and dUMP as substrates, but this was not so when dUMP was replaced by dTTP. Unlike the mouse enzyme, the human enzyme in the transformants did not co-sediment with DNA polymerase alpha and thymidine kinase in a sucrose gradient, suggesting that the human enzyme is not incorporated into a multienzyme complex for DNA replication. The high levels of the human enzyme in the transformants were suppressed to various degrees by fusion with a wild type mouse line. No active hybrid dimer enzyme was found between the human and mouse enzymes, which each consist of two identical subunits. Thus, the human enzyme in the transformants seems to behave differently from the mouse enzyme and its overproduction seems to be necessary for supporting the normal growth of the transformants.
...
PMID:Unusual aspects of human thymidylate synthase in mouse cells introduced by DNA-mediated gene transfer. 684 16

It is presumed that the dGTP and dATP needed for replicative DNA synthesis can be formed by way of either ;salvage' pathways or biosynthesis de novo. This was examined by adding hydroxyurea to cultures of rat thymus cells to inhibit ribonucleoside diphosphate reductase, a key enzyme of the ;de novo' pathway. Most of the inhibition of the incorporation of [Me-(3)H]thymidine and deoxy[5-(3)H]cytidine by low concentrations of hydroxyurea (100-500mum) was prevented by substrates of the salvage pathway (400mum-deoxyguanosine and, to a lesser extent, 200mum-deoxyadenosine). However, isotope-dilution studies indicated that the purine deoxyribonucleosides prevented inhibition by decreasing pyrimidine deoxyribonucleotide competitor pools. Evidence was obtained that a hydroxyurea-induced increase in the thymidine-competitor pool (probably dTTP) was prevented to an equal extent by deoxyguanosine and by the inhibitor of thymidylate synthase, deoxy-5-fluorouridine. These compounds had almost identical effects on hydroxyurea dose-response curves and on thymidine isotope-dilution plots. The evidence suggests that exogenous purine deoxyribonucleosides cannot prevent the inhibition by hydroxyurea of thymus-cell DNA synthesis. This could mean that, with respect to the metabolism of purine deoxyribonucleotides, ribonucleoside diphosphate reductase is tightly coupled to DNA polymerase in a multienzyme complex. The complex would not permit entry of exogenous metabolic intermediates into the ;de novo' pathway, but would still be subject to the regulatory effects of these intermediates. Thus dGTP and dATP formed from exogenous purine deoxyribonucleosides by salvage pathways might deplete pyrimidine deoxyribonucleotide competitor pools by inhibiting relatively hydroxyurea-insensitive activities of ribonucleoside diphosphate reductase.
...
PMID:Isotope-dilution analysis of the effects of deoxyguanosine and deoxyadenosine on the incorporation of thymidine and deoxycytidine by hydroxyurea-treated thymus cells. 697 May 75

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.
...
PMID:The effect of cyclic nucleotides on DNA polymerase, thymidylate synthetase, thymidine kinase and deoxynucleoside levels of Waler carcinoma. 718 96

The major effect of eupaformosanin as an antineoplastic agent on Ehrlich ascites cell metabolism was to inhibit deoxyribonucleic acid synthesis, specifically at deoxyribonucleic acid polymerase and thymidylate synthetase enzymatic sites. Both pyrimidine and purine systems of Ehrlich ascites were marginally inhibited. Ribonucleic acid synthesis and messenger and ribosomal polymerase activities also were suppressed. Cyclic adenosine monophosphate levels were increased significantly, which correlated with the drastic reduction of histone phosphorylation. Eupaformosanin also suppressed a number of glycolytic and Krebs cycle enzymes as well as oxidative phosphorylation in vitro. All of the inhibited enzymes are known thiol-bearing enzymes that can undergo a Michael-type addition with the alpha-methylene-gamma-lactone moiety of eupaformosanin, as shown with other sesquiterpene lactones.
...
PMID:Antitumor agents XLI: Effects of eupaformosanin on nucleic acid, protein, and anaerobic and aerobic glycolytic metabolism of Ehrlich ascites cells. 738 5


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---