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 RNA-dependent DNA polymerase purified from B77 avian sarcoma virus exhibited two distinct DNA-processing activities. The alpha and beta 2 isoenzymes possessed an endodeoxyribonuclease activity capable of nicking simian virus 40 superhelical DNA, whereas the alpha beta isoenzyme performed as an untwisting topoisomerase. Both activities associated with the three molecular forms of the retroviral DNA polymerase were dependent on the presence of either Mn2+ or Mg2+ ions. From analysis of the denaturated DNA products, it is apparent that the alpha and beta 2 isoenzymes introduced two nicks, one per each strand in the superhelical simian virus 40 DNA molecules, whereas the alpha beta polymerase converted these supercoiled molecules to the relaxed covalently closed circular form. The notion that the DNA-processing activities are located on the DNA polymerase molecules was supported by the following: (i) the three isoenzymes were of a high purity; (ii) the activities cosedimented in glycerol gradients with the DNA polymerase activities of the alpha, beta 2, and alpha beta molecular forms; and (iii) immunoglobulin directed against the purified polymerase immunoprecipitated the DNA-processing activities. Chemical treatments of the DNA polymerase molecules (with pyridoxalphosphate, iodoacetamide, and sulfhydryl reagents), which inhibited the polymerase activity, also suppressed the endonucleolytic and topoisomerase activities, suggesting that cystein and amino groups play an important role in the active sites of the DNA-processing activities as well.
...
PMID:DNA-processing activities associated with the purified alpha, beta 2, and alpha beta molecular forms of avian sarcoma virus RNA-dependent DNA polymerase. 617 42

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

The purified type II DNA topoisomerase from the embryos of Drosophila melanogaster exists in its native form as a dimer of 170,000-dalton polypeptides. In addition to the 170,000-dalton polypeptides, 3 polypeptides with molecular weights of 151,000, 141,000, and 132,000 were resolved when the enzyme was analyzed by electrophoresis under denaturing conditions. All four polypeptides can participate in the topoisomerase cleavage reaction and form covalent complexes with the cleaved DNA. Furthermore, immunochemical and biochemical data showed that they are structurally related and, therefore, the smaller polypeptides are likely generated from the 170,000-dalton polypeptide by proteolysis. The double strand DNA cleavage reaction of Drosophila topoisomerase has different site specificity from the Escherichia coli DNA gyrase-effected reaction. However, they result in an identical DNA structure at the cleavage site, which is a staggered double strand break with 4-nucleotide long 5'-protruding ends. The 3'-ends at the site of cleavage by Drosophila topoisomerase II have free hydroxyl groups and can be extended by exactly 4 nucleotides with T4 DNA polymerase, while the 5'-ends are covalently linked to the topoisomerase molecules. This similarity in cleavage site structure for Drosophila topoisomerase II and E. coli DNA gyrase suggests that they share some fundamental features in their mechanism of action.
...
PMID:Double strand DNA cleavage by type II DNA topoisomerase from Drosophila melanogaster. 630 84

A protein required for the elongation of replicating intermediates of adenovirus (Ad) DNA to full length has been isolated and characterized. This factor, isolated from nuclear extracts of uninfected HeLa cells, has been designated nuclear factor II. In the presence of Ad DNA with proteins at each 5' end (Ad DNA-protein) and three proteins coded for by the Ad genome [the preterminal protein (pTP), the DNA polymerase (Ad Pol), and the DNA binding protein (Ad DBP)], nuclear factor II complementing activity is detected only in the presence of host nuclear factor I. Highly purified preparations of nuclear factor II that are free of detectable DNA polymerase alpha, beta, and gamma activities contain a DNA topoisomerase activity. Furthermore, type I DNA topoisomerases purified from HeLa cells and calf thymus substitute for nuclear factor II complementing activity in the in vitro Ad DNA replication system. These results indicate that a protein that is involved in higher order DNA structure is required for Ad replication. This protein plus the purified proteins described above carry out the initiation and synthesis of full-length 36,000-base-pair Ad DNA.
...
PMID:Adenovirus DNA replication in vitro: synthesis of full-length DNA with purified proteins. 630 11

A DNA-relaxing enzyme was found to copurify along with herpes simplex virus type I (HSV-1)-induced DNA polymerase throughout a multistep purification scheme. Both the enzymes had similar sedimentation velocity, required high ionic strength for optimal enzymatic activities and showed time dependence of reaction. The DNA-relaxing enzyme however, differed from the HSV-1 DNA polymerase in its requirement for higher Mg2+ concentration, rATP and much broader pH dependence. Furthermore, phosphonoacetic acid, a potent inhibitor of HSV-1 DNA polymerase did not influence the DNA-relaxing activity even at a much higher concentration. On the other hand, the DNA-relaxing enzyme associated with the DNA polymerase may be specified by HSV-1 since IgG fraction of rabbit antisera against the virus-infected cells but not against the mock-infected cells strongly inhibited both the enzymatic activities. Thus, HSV-1-induced DNA polymerase which is known to be associated with a 3' to 5' exonuclease may also be associated with yet another enzymatic activity involved in DNA metabolism.
...
PMID:A DNA topoisomerase activity copurifies with the DNA polymerase induced by herpes simplex virus. 630 34

We investigated, in a cloned hamster tracheal epithelial cell line HTE-B, the effects of inhibitors of DNA topoisomerase, novobiocin and nalidixic acid; of DNA polymerase, 1-beta-arabinofuranosylcytosine (ara-C) and 2',3'-dideoxythymidine; of ribonucleotide reductase, hydroxyurea; and of poly(ADP-ribose)synthetase, 3-aminobenzamide, upon the removal of benzo[a]pyrene adducted to DNA [B[a]P--DNA]. A substantial reduction in the rate of removal of the polycyclic hydrocarbon-adducts occurred when nalidixic acid was added to the HTE-B cells that had been previously incubated with B[a]P for 8 h. Novobiocin produced a similar, but less marked, effect. The rate of disappearance of the individual B[a]P--DNA adducts was measured by analysis of the h.p.l.c. profiles. Of the 5 major adducts observed under the h.p.l.c. conditions, 4 were reduced in control cells to 30% of the original levels by 24 h after removal of the B[a]P from the medium; adduct 5 was almost completely removed. In the presence of nalidixic acid, during the 24 h repair period, only the removal of adduct 5 was unimpaired; the removal of the other 4 adducts was significantly retarded. On the other hand, 3-aminobenzamide addition did not affect the rate of removal of B[a]P--DNA adducts from the HTE-B cells. We employed the combinations of ara-C and dideoxythymidine or ara-C and hydroxyurea to allow the accumulation of single strand breaks after incubation of the HTE-B cells with B[a]P. These breaks were assayed by alkaline elution analysis. Inclusion of these inhibitors during the 2 h after removal of the B[a]P from the medium resulted in the accumulation of 4-5 single strand breaks/10(10) daltons of HTE-B DNA. This compares with a minimum estimate of the number of adducts removed during this period of 3 adducts/10(7) daltons. This discrepancy may indicate that the majority of lesions are not repaired by a pathway sensitive to polymerase inhibitors. In the presence of 3-aminobenzamide, we routinely observed a 10% increase in the alkaline elution of the DNA obtained from B[a]P-treated cells (1-2 breaks/10(10) daltons). Our results indicate that an excision repair process may be involved in the removal of at least some of the B[a]P-induced damage to DNA. However, the repair of the multiple adducts is complex and may involve pathways other than classical excision repair.
...
PMID:The influence of inhibitors on the repair of benzo[a]pyrene-damaged DNA in hamster tracheal epithelial cells. 632 Oct 50

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

At an early purification stage, DNA polymerase alpha holoenzyme from calf thymus can be separated into four different forms by chromatography on DEAE-cellulose. All four enzyme forms (termed A, B, C, and D) are capable of replicating long single-stranded DNA templates, such as parvoviral DNA or primed M13 DNA. Peak A possesses, in addition to the DNA polymerase alpha, a double-stranded DNA-dependent ATPase, as well as DNA topoisomerase type II, 3'-5' exonuclease, and RNase H activity. Peaks B, C, and D all contain, together with DNA polymerase alpha, activities of primase and DNA topoisomerase type II. Furthermore, peak B is enriched in an RNase H, and peaks C and D are enriched in a 3'-5' exonuclease. DNA methylase (DNA methyltransferase) was preferentially identified in peaks C and D. Velocity sedimentation analyses of the four peaks gave evidence of unexpectedly large forms of DNA polymerase alpha (greater than 11.3 s), indicating that copurification of the above putative replication enzymes is not fortuitous. With moderate and high concentrations of salt, enzyme activities cosedimented with DNA polymerase alpha. Peak C is more resistant to inhibition by salt and spermidine than the other three enzyme forms. These results suggest the existence of a leading strand replicase (peak A) and several lagging strand replicase forms (peaks B, C, and D). Finally, the salt-resistant C form might represent a functional DNA polymerase alpha holoenzyme, possibly fitting in a higher-order structure, such as the replisome or even the chromatin.
...
PMID:Mammalian DNA polymerase alpha holoenzymes with possible functions at the leading and lagging strand of the replication fork. 658 75

A preparation of bacteriophage T4-induced deoxyribonucleotide synthetase complex is described. This very large complex of enzymes can be separated by centrifugation at 100,000 X g, by sucrose step gradient centrifugation, or with molecular exclusion columns. By direct assay and by unidimensional and two-dimensional acrylamide electrophoretic separations the following T4-coded enzymes were shown to be associated with the complex: ribonucleoside diphosphate reductase, dCMP deaminase, dCTP/dUTPase, dCMP hydroxymethylase, dTMP synthetase, and DNA polymerase. Other phage-coded prereplicative proteins related to DNA replication and other phage functions such as the proteins coded by genes 32, 46, rIIA, and rIIB as well as many unidentified proteins were also consistently associated with the isolated fractions. T4 DNA topoisomerase, a membrane-bound enzyme, was found in quantity in all purified fractions of the complex, even in preparations apparently free of membrane and of T4 DNA. The functional integrity of a segment of the complex was followed by measuring the conversion of [5-3H]CDP to the level of 5-hydroxymethyl dCMP. This series of reactions requires the actions of T4-coded ribonucleoside diphosphate reductase and its associated reducing system, dCTP/dUTPase and dCMP hydroxymethylase, 3H being lost to water at the last step. In this reaction sequence an intermediate, [5-3H]dCMP, is maintained at low steady state concentrations, and argument is presented that the synthesis of deoxyribonucleotides is channeled and normally tightly coupled to DNA replication. One of the primary characteristics of this complex is its ready dissociation of dilution into smaller complexes of proteins and to the free forms of the proteins. That the complex is held together by weak electrostatic forces was supported by its sensitivity to dissociation at moderate salt concentrations. Not only the enzymes required in deoxyribonucleotide synthesis but T4 DNA polymerase, T4 DNA topoisomerase, and a number of other proteins dissociate to varying degrees from the larger complexes under these conditions.
...
PMID:Characteristics of a bacteriophage T4-induced complex synthesizing deoxyribonucleotides. 675 52

Frameshift mutations induced by acridines in bacteriophage T4 have been shown to be due to the ability of these mutagens to cause DNA cleavage by the type II topoisomerase of T4 and the subsequent processing of the 3' ends at DNA nicks by DNA polymerase or its associated 3' exonuclease followed by ligation of the processed end to the original 5' end. An analysis of the ability of nick-processing models is presented here to test the ability of nick processing to account for the DNA sequences of duplications and deletions induced in the aprt gene of CHO cells by teniposide (VM-26) [Han et al. (1993) J. Mol. Biol., 229, 52]. Although teniposide is not an acridine, it induces topoisomerase II-mediated DNA cutting in aprt sequences in vitro and mutagenesis in vivo. Although the previous study noted a correlation between mutation sites and nearby DNA discontinuities induced by the enzyme in vitro, neither the nick-processing model responsible for T4 mutations, nor double-strand break models alone were able to account for most of the mutant sequences. Thus, no single model explained the correlation between teniposide-induced DNA cleavage and mutagenic specificity. This report describes an expanded analysis of the ways that nick-processing models might be related to mutagenesis and demonstrates that a modified nick-processing model provides a biochemical rationale for the mutant specificities. The successful nick-processing model proposes that either 3' ends at nicks are elongated by DNA polymerase and/or that 5' ends of nicks are subject to nuclease activity; 3'-nuclease activity is not implicated. The mutagenesis model for nick-processing of teniposide-induced nicks in CHO cells when compared to the mechanism of nick-processing in bacteriophage T4 at acridine-induced nicks provides a framework for considering whether the differences may be due to cell-specific modes of DNA processing and/or due to the precise characteristics of topoisomerase-DNA intermediates created by teniposide or acridine that lead to mutagenesis.
...
PMID:Deletion and duplication sequences induced in CHO cells by teniposide (VM-26), a topoisomerase II targeting drug, can be explained by the processing of DNA nicks produced by the drug-topoisomerase interaction. 751 Aug 33


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---