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

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Query: EC:2.7.7.49 (reverse transcriptase)
31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The B95-8 cell line, a widely used source of highly transforming Epstein-Barr virus (EBV), obtained from the laboratory of origin, harbored an infectious retrovirus. This retrovirus generally resembled the Type D retroviruses structurally and developmentally and like the Type D retroviruses preferred Mg2+ to Mn2+ in its RNA-directed DNA polymerase reaction. Evidence for the presence of retrovirus was found in B95-8 cultures from two other sources within the United States, either by assay for polymerase or by electron microscopy. Comparison of two B95-8 cell lines showed cytogenetic differences as well as differences in retroviral activities. The results suggest that any B95-8 culture should be tested for the presence of retrovirus before its use as a source of EBV.
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PMID:Presence of retrovirus in the B95-8 Epstein-Barr virus-producing cell line from different sources. 608 97

The characteristics of the virion-associated RNA-dependent DNA polymerase (RDPase) of a baboon endogenous virus, M7, were studied extensively; the optimal conditions for the exogenous RDPase reaction were obtained with 0.4 mM-Mn2+, 110 mM-NaCl, 24 microgram/ml poly(rA). oligo(dT)12-18, at pH 7.6 in the presence of 0.01 % Brij-58. Under these conditions, the incorporation of 3H-TMP proceeded up to 90 min at a speed of 0.1 pmol TMP/microgram virus protein/min. Poly(rC). oligo (dG)12-18 and poly(rCm). oligo (dG)12-18 served as the template-primers in the exogenous reaction with 3 mM-Mg2+ and 0.4 mM-Mn2+, respectively. Polyuridylic acid, bleomycin, rifampicin, spermidine and inorganic phosphate significantly inhibited the RDPase activity of BaEV. The RDPase of BaEV requires a higher concentration of NaCl, a lower pH and milder conditions of detergent treatment than those of other mammalian retroviruses.
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PMID:The characteristics of the RNA-dependent DNA polymerase of baboon endogenous virus. 615 24

An RNA-dependent DNA polymerase was isolated from purified virions of endogenous oncornaviruses released by the MOPC-315 murine myeloma cell line. Upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the purified enzyme was found to consist of two major polypeptides with molecular weights of about 28,000 and 26,500. The active enzyme had a molecular weight of approximately 56,000, as calculated from its sedimentation on glycerol density gradients, indicating that it is probably a dimer of the two subunit polypeptides. The isolated MOPC-315 virus polymerase exhibited all three activities known to be found in the DNA polymerase from oncornaviruses, namely, an RNA-dependent DNA polymerase, a DNA-dependent DNA polymerase, and an RNase H. The RNA-dependent polymerase activity showed a prounced preference for Mn2+ over Mg2+, whereas the DNA-dependent and RNase H reactions were catalyzed by these two cations to an almost equal extent. The purified polymerase was found to be immunologically related to the polymerase of Rauscher murine leukemia virus.
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PMID:RNA-dependent DNA polymerase of an endogenous type C virus of mice: purification and partial characterization. 615 78

In vitro DNA synthesis on a phi X174 template primed with a restriction fragment and catalyzed by the Escherichia coli DNA polymerase I large (Klenow) fragment (pol I) terminates at the nucleotide preceding a site that has been altered by ultraviolet irradiation or treatment with N-acetylaminofluorene. Termination on ultraviolet-irradiated templates is similar when synthesis is catalyzed by E. coli DNA polymerase III holoenzyme (pol III), phage T4 DNA polymerase, a polymerase alpha from human lymphoma cells, or avian myeloblastosis virus reverse transcriptase. 3' leads to 5' exonuclease activity cannot be detected in the reverse transcriptase and DNA polymerase alpha preparations. On N-acetylaminofluorene templates, pol I, pol III, and T4 polymerase reactions terminate immediately preceding the lesion, whereas reverse transcriptase-catalyzed reactions and, at some positions in the sequence, polymerase alpha-catalyzed reactions terminate at the site of the lesion. Substitution of Mn2+ for Mg2+ changes the pattern of pol I-catalyzed termination sites. The data suggest that termination is a complicated process that does not depend exclusively on the 3' leads to 5' exonuclease activity associated with many polymerases.
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PMID:Sites of termination of in vitro DNA synthesis on ultraviolet- and N-acetylaminofluorene-treated phi X174 templates by prokaryotic and eukaryotic DNA polymerases. 616 85

The Mn2+-dependent endonuclease activity associated with the avian myeloblastosis virus RNA-directed DNA polymerase has been shown to be activated by ATP in the presence of Mg2+. In the presence of Mn2+ the endonucleolytic activity was stimulated about 3-fold by the addition of ATP. The earlier identified Mr = 40,000 Friend murine leukemia virus (F-MuLV)-associated endonuclease which functions in the presence of both Mg2+ and Mn2+ has also been shown to be similarly stimulated by ATP. For both endonuclease activities stimulation was only observed at ATP concentrations above 0.5 mM, and it did not increase upon elevating the ATP concentration above 2.5 mM. ADP and dATP also stimulated both activities, although not to the same extent as ATP. GTP had no apparent effect and AMP seemed to inhibit both activities. The effect ATP analogs had on the F-MuLV associated endonuclease activity could suggest that the endonuclease reaction in the presence of ATP might involve the cleavage of beta-gamma phosphate bonds in ATP. Neither adenyl-5'-yl imidodiphosphate nor (beta, gamma-methylene)adenosine 5'-triphosphate stimulated the activity, whereas significant stimulation was observed in the presence of (alpha, beta-methylene)adenosine 5'-triphosphate. Although no ATPase activity could be detected in the purified F-MuLV endonuclease preparation, the data do not exclude the possibility that ATP may be cleaved in amounts which are equivalent to the number of nicks introduced into DNA by the virus-associated endonuclease. In the presence of ATP and Mg2+ the F-MuLV-associated endonuclease nicked both supercoiled and linear DNA duplexes extensively, although the former was nicked more readily than the latter. Single-stranded DNA functioned poorly as a substrate. The nicks introduced by the enzyme contained a 5'-phosphoryl terminus and a 3'-hydroxyl group.
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PMID:Effect of ATP on the Friend Murine leukemia virus-associated endonuclease activity and the endonuclease activity of the avian myeloblastosis virus RNA-directed DNA polymerase. 616 71

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.
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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

The structural proteins as well as some features of the RNA-dependent DNA polymerase of the hamster endogenous retrovirus (HaER) were examined. The polypeptide pattern of this virus is substantially different from that of other known retroviruses in containing major polypeptides with molecular weights of 68,000, 59,000, 27,000 and 24,000 daltons. Double antibody competitive radioimmunoassays showed that the HaER particles do not share any detectable antigenic relatedness with the murine viruses' p30, but manifest a considerable relatedness with the feline leukemia virus p27 and a slight cross-reactivity with the rat virus major protein. The RNA-dependent DNA polymerase of HaER virus has a molecular size of approximately 73,000 daltons and in contrast to other mammalian retroviruses shows no significant preference for Mn2+ over Mg2+. Apart from the lack of antigenic relatedness between the HaER virus proteins and the p30 protein of murine viruses, there is also no antigenic relatedness between HaER and murine viruses insofar as their DNA polymerase is concerned.
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PMID:Hamster endogenous retrovirus (HaER)--distinct properties of structural proteins and DNA polymerase. 619 53

RNA-dependent DNA-polymerase was isolated from rat liver, and its characteristics were studied. Wistar rat livers were homogenized in the disruptive buffer, centrifuged at 100,000 g and the supernatant was freed of the nucleic acids by DEAE-cellulose (DE-23) chromatography. The further chromatography of the eluate on DEAE-cellulose (DE-52) and phosphocellulose P-11 resulted in the obtaining of 300-400-fold purified RNA-dependent DNA-polymerase. Even more purified enzyme 1500-fold was isolated from the 165,000 g pellet of postmitochondrial rat liver fraction. The main properties of the purified enzyme are characteristic for the retroviral reverse transcriptase. The enzyme catalyzes DNA synthesis when poly(A)+mRNA is used as a template-primer. Its sedimentation constant amounts to 4.6 S. Mg2+ is preferable to Mn2+ as an activator of the enzyme. The optimal pH is 7.8. Among the products of the enzymic reaction hybrid RNA X DNA molecules were identified.
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PMID:[RNA-dependent DNA polymerase from rat liver]. 620 92

Infectious retroviruses have been detected in 22 of 45 randomly selected patients with acquired immune deficiency syndrome (AIDS) and in other individuals from San Francisco. The AIDS-associated retroviruses (ARV) studied in detail had a type D morphology, Mg2+-dependent reverse transcriptase, and cytopathic effects on lymphocytes. The viruses can be propagated in an established adult human T cell line, HUT-78. They cross-react with antiserum to the lymphadenopathy-associated retrovirus isolated from AIDS patients in France. Antibodies to ARV were found in all 86 AIDS patients and in a high percentage of 88 other homosexual men in San Francisco. This observation indicates the widespread presence of these lymphocytopathic retroviruses and their close association with AIDS.
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PMID:Isolation of lymphocytopathic retroviruses from San Francisco patients with AIDS. 620 63

We have examined the effect of DNA lesions, which in vivo are potentially mutagenic, on in vitro DNA synthesis carried out by a number of purified DNA polymerases using a 0X174 template. Both acetyl aminofluorene (AAF) adducts and UV-induced pyrimidine dimers are blocks to elongation by DNA polymerases. On UV-irradiated DNA templates synthesis terminates one nucleotide before the sites of pyrimidine dimers with all of the enzymes tested: Pol I and Pol III holoenzyme from Escherichia coli, T4 DNA polymerase, avian myeloblastosis virus reverse transcriptase and a mammalian DNA polymerase alpha. With AAF, which reacts at the C-8 position of guanine, differences are observed between the above enzymes, with the latter two inserting a nucleotide opposite the site of the lesion. Substitution of Mn2+ for Mg2+ as the cation in the Pol I reactions causes changes in the termination pattern on both UV-irradiated and AAF-reacted templates. The significance of these results to the process of inducible error-prone repair and the possible bypass of lesions in the DNA is discussed.
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PMID:In vitro replication of mutagen-damaged DNA: sites of termination. 621 48


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