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)

The induction of erythroid differentiation in the T3-C12 clone of Friend leukemia cells by dimethyl sulfoxide is accompanied by reduction in viral RNA-dependent DNA polymerase activity with increased cellular delta-aminolevulinic acid synthetase activity and hemoglobin synthesis. These cells were treated with a variety of compounds to determine whether other durgs are capable on inducing erythroid differentiation. While several hormones, inhibitors of RNA synthesis, organic solvents, inhibitors of DNA polymerase, sulfhydryl inhibitors, and inducers of delta-aminolevulinic acid synthetase administered singly did not stimulate hemoglobin synthesis like dimethyl sulfoxide, inhibitors of DNA and RNA synthesis such as adriamycin, mitomycin C, and hydroxyurea:mithramycin were synergistic in stimulating erythroid differentiation.
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PMID:Erythroid differentiation in cultured Friend leukemia cells treated with metabolic inhibitors. 5 26

A line of hamster cells transformed by SV40 (TSV5 clone 2) contains different DNA polymerase activities. One of them has the same template specificity as viral reverse transcriptases. Partial isolation of R-type virus-like particles from TSV5 clone 2 shows that a reverse transcriptase activity is associated with these RNA viruses. This reverse transcriptase was partially purified and its biochemical properties are described.
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PMID:Reverse transciptase activity associated with R-type virus-like particles of SV40-transformed hamster cells (TSV5 clone 2). 5 43

Endogenous ecotropic type C viruses were induced by iodedeoxyuridine from nontransformed and chemically or spontaneously transformed clones of the C3H/10T1/2 cell line. Viruses produced by cells of certain transformed clones were N-tropic and formed large XC plaques. In contrast, viruses produced by nontransformed C3H/10T1/2 cells were not detectable in the XC plaque test. These XC- viruses infected mouse cells with high efficiency, as shown by the induction of murine leukemia virus group-specific antigens in infected cells, but virus production, as determined by DNA polymerase-containing particles, was extremely low. Upon growth in certain mouse cells these replication-deficient, XC(-) viruses converted to type C viruses that were similar in XC assays to N-tropic AKR virus (XC+).
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PMID:Endogenous ecotropic mouse type C viruses deficient in replication and production of XC plaques. 5 71

We have examined the location, structure, and mechanism of synthesis of unintegrated viral DNA present in fully transformed cultures of avian sarcoma virus-infected duck cells. De novo synthesis of the unintegrated forms several weeks after the initial infection was documented by labeling unintegrated DNA in both strands with 5-bromodeoxyuridine. The unintegrated DNA is synthesized in, and probably confined to, the cytoplasm, and it consists of duplexes of short "plus" strands (ca. 0.5 X 10(6) to 1.0 X 10(6) daltons) and "minus" strands the length of a subunit of the viral genome (ca. 2.5 X 10(6) to 3.0 X 10(6) daltons). The structure of the duplex and the mode of incorporation of density label support the hypothesis that the unintegrated DNA is synthesized from an RNA templated by virus-coded DNA polymerase.
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PMID:Unintegrated viral DNA is synthesized in the cytoplasm of avian sarcoma virus-transformed duck cells by viral DNA polymerase. 5 74

Storage of the dimeric (alphabeta) form of avian myeloblastosis virus (AMV) DNA polymerase in glycerol resulted in the release of the smaller alpha subunit, as detected by glycerol gradient sedimentation. Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of enzyme stored in glycerol showed the concomitant appearance of several polypeptides and a lowering in the level of both beta and alpha components. This reduction appears to be the result of cleavages introduced by traces of hydrolytic activity present in glycerol samples. An enhancement of alpha subunit released, as detected by activity profile, was also achieved upon direct but limited exposure of purified avian myeloblastosis virus DNA polymerase to carboxymethyl-cellulose-bound trypsin matrix. Electrophoretic analysis of digested enzyme revealed a progressive fragmentation, with simultaneous increase in the alpha subunit and decrease in the beta subunit.
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PMID:Mechanism of release of active alpha subunit from dimeric alpha beta avian myeloblastosis virus DNA polymerase. 5 80

We have compared the relative merits of several procedures for the isolation of RNA-directed DNA polymerase (EC 2.7.7.7.) from cells using a reconsituted model system consisting of a mixture of woolly monkey (simian) sarcoma virus and a cultured human lymphoblastoid cell line, NC-37. When the cell-virus mixture was gently disrupted and fractionated by differential centrifugation, most of the added polymerase was recovered associated with a particulate fraction obtained from the post-mitochondrial supernatant. Purification of the polymerase was best achieved starting from this fraction. The particulate fraction itself can be purified by gel filtration through a Sepharose 2 B column. This procedure did not significantly alter the composition of viral and cellular DNA polymerases. Whereas as little as 7.5 - 10(5) viral particles were sufficient for the detection of RNA-directed DNA polymerase activity, a minimum of about 10(11) particles were necessary for the isolation and unequivocal characterization of the enzyme from the cell-virus mixture by subcellular fractionation and chromatographic separation from cellular DNA polymerases. Purified RNA-directed DNA polymerase had the same primer-template characteristics, sedimentation properties, and immunological cross reactivity as the enzyme purified from density gradient-banded virions of simian sarcoma virus. Methods involving total extraction of the cell-virus mixture either by repeated freezing and thawing followed by detergent treatment or by Dounce homogenization and treatment with high salt and detergent failed to provide RNA-directed DNA polymerase free of cellular DNA polymerases. Because of this, low levels of cellular RNA-directed DNA polymerase may be missed when these approaches are used.
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PMID:A comparative evaluation of methods for isolation of RNA-directed DNA polymerase from cells in a reconstituted system. 5 69

The alkoxybenzophenanthridine alkaloids (coralyne acetosulfate, fagaronine chloride, and nitidine chloride) have been reported to possess antileukemic activity in mice. These compounds were tested for inhibition of reverse transcriptase activity of an RNA tumor virus and DNA polymerase, RNA polymerase, and polyadenylic acid polymerase activities of NIH-Swiss mouse embryos. Reverse transcriptase and DNA polymerase activities were strongly inhibited by these antileukemic alkaloids, whereas RNA polymerase and polyadenylic acid polymerase activities were only moderately affected. Viral and cellular DNA polymerase activities were potently diminished by the alkaloids when poly[d(A-T)], poly(dA)-oligo(dT), and poly(rA)-oligo(dT) template primers were used in the reaction mixture; however, no inhibition of enzyme activity was obtained with poly(rC)-oligo(dG) as template primer. These results suggest that alkoxybenzophenanthridine alkaloids inhibit DNA polymerase activity by interaction with A:T base pairs of the template primer.
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PMID:Inhibition of mammalian and oncornavirus nucleic acid polymerase activities by alkoxybenzophenanthridine alkaloids. 5 19

In the post-mitochondrial fraction of murine LBN/b leukemic cells, four fractions with DNA polymerase activity (I, II, III, IV) were found. On the basis of ion exchanger affinity and poly(A), poly(C) and poly(Cm) replication ability, fraction I was classified as RNA-directed DNA polymerase of viral origin. On the basis of the differences in the ion exchanger affinity, molecular weight, template requirement, pH-dependence of enzymatic activity and NaCl concentration, divalent ion requirements and susceptibility to N-ethylmaleimide inhibition, fractions II, III and IV were classified as DNA-directed DNA polymerases beta, alpha and gamma, respectively. Three fractions, i.e. reverse transcriptase, and DNA-directed DNA polymerases beta and gamma, were found to incorporate dTMP on a poly(A)-oligo(dT) template-primer. Despite the similarity of the reaction of DNA polymerases beta and gamma with poly(A)-oligo(dT), some other properties of these enzymes suggest that they represent distinct enzymatic entities.
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PMID:DNA polymerases of murine LBN/b leukemic cells. 5

The possible role of DNA polimerase III in conjugation was studied in a series of mutants temperature-sensitive for DNA polymerase III synthesis. The temperature-sensitive DNA mutation called dnaE 486 (ts) prohibits vegetative DNA replication at 41-45 degrees. Transfer of episome and chromosome from temperature-sensitive donor, carrying dnaE mutation to wild-type recipient strains, revertants and dnaE recipients was investigated. In the first two cases the number of Lac+ sexductants being even slightly higher at 43 degrees. Conjugational synthesis accompanying transfer involving the combination of dnaE (ts) thymine dependent and thymine independent donor and recipient strains measured by incorporation of 14C thymine was observed at the restrictive temperature. In the case of conjugation with temperaturesensitive recipient strains a drop of Lac+ sexductants and Pro+ recombinants may be as a result of disturbances in the synthesis of complementary strand in recipient, known to be dependent on pol III. However, the episome investigated by centrifugation in neutral CsC1 gradient after its transfer to the recipient with faulty polymerase III was double stranded (replicated) at the restrictive temperature.
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PMID:The role of polymerase III in conjugation between E. coli K12 donor and recipient strains carrying dnaE ts mutation. 5 32

Several human prostatic tissues have been examined for possible particles and associated DNA polymerizing activity generally associated with the C-type RNA tumor virus family. Partially purified tissue extracts, when centrifuged to equilibrium in sucrose gradients, yield fractions which contain actinomycin D resistant, endogenous DNA polymerase activity; this activity bands at a density of 1.15-1.18 gm/cm3. Further analysis of the endogenous products by sucrose gradient sedimentation suggested the presence of high molecular weight RNA:DNA hybrids generally felt to be indicative of a faithful copy of a lengthy stretch of viral specific RNA. However, most of the DNA products synthesized in these endogenous reactions sedimented in much lower molecular weight regions of these sucrose gradients. Clearly, the relative distributions of "high" and "low" molecular weight products could critically depend on the nuclease content of the subcellular fraction under study, and the prostate may be relatively enriched in nucleases. Further, oligo (dT) stimulated the endogenous DNA polymerase activity contained in these extracts, and omission of one of the DNA precursor nucleotides depressed it. Thus, it seems unlikely that terminal transferase activity, rather than genuine DNA polymerization, was being measured primarily. Because of the spectrum of molecular weight classes formed by these DNA:RNA hybrids, as well as their apparent presence in normal prostatic tissue, we find it difficult to ascribe their presence with certainty either to the presence of typical C-type RNA viruses or to the exclusive behavior of the neoplastic prostatic tissue. Thus, our studies lend support to the growing evidence for functions similar to those of C-type RNA viruses being relatively widespread in human tissues without the apparent necessity for a possible etiologic role in neoplastic production (Strand and August, 1974; Sherr et al., 1974). At the same time, our current studies emphasize the need for caution in drawing conclusions from results utilizing probes generally felt quite useful in scoring for presence of virus in lower animals at least in the human prostate.
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PMID:RNA tumor virus-like activities in human solid tissues: endogenous RNA:DNA polymerase activities in the prostate. 5 36


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