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 new antiviral substance phosphonoformate (PFA) has been tested in a cell-free system for its effect on reverse transcriptases from an avian retrovirus (avian myeloblastosis virus, AMV) and from mammalian retroviruses (Rauscher leukaemia virus, RMuLV; bovine leukaemia virus; baboon endogenous virus; simian sarcoma virus; visna virus). The observed inhibitory effect of PFA has been compared with that of a structurally related substance, phosphonoacetate (PAA). Phosphonoformate, at a concentration of 100 microM, reduced the activities of all the above mentioned polymerases by 90% when (rA)n.(dT)10 was used as a template/primer. The dose-response curves for AMV and RMuLV polymerases primed with (rA)n.(dT)10 showed PFA to be a 1000-fold more active than PAA; the RMuLV polymerase activity was reduced to 50% after incubation with 0.7 microM-PFA and 0.7 mM-PAA, respectively. There was no difference in PFA inhibition of virus-associated and purified reverse transcriptase activity. Results with various synthetic templates showed that both the RNA- and the DNA-dependent polymerase activities of reverse transcriptase were inhibited by PFA. The endogenous polymerase activity of AMV was inhibited to 50% at 100 microM-PFA, while PAA had no effect. The PFA inhibition was dependent on whether Mg2+ or Mn2+ was used as divalent cation in the assay. Phosphonoformate arrested DNA synthesis immediately after being added to the assay system. The mechanism of inhibition of the AMV polymerase was non-competitive with respect to substrate and template and the apparent inhibition constants were 16 microM and 9 microM, respectively.
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PMID:Phosphonoformate inhibits reverse transcriptase. 9 44

A procedure was established whereby most of the major viral proteins were isolated to apparent homogeneity in biologically and immunologically active forms from a single batch of avian sarcoma virus QV2. For the initial step of purification, gently disrupted virions were fractionated by CsCl centrifugation into envelope proteins, RNA-dependent DNA polymerase, and viral core proteins. Further purification of envelope glycoproteins and DNA polymerase was performed by affinity chromatography on agarose columns cross-linked with plant lectins and poly(C), respectively. On the other hand, core proteins were fractionated by a combination of gel filtration and ion-exchange column chromatography into components p27, p19, and p15. The core protein p15 thus isolated retained proteolytic activity even after storage for 6 months. The present study also demonstrated that QV2 p19 is structurally altered from the corresponding protein of avian myeloblastosis virus (AMV), a reference avian leukosis-sarcoma virus having a well-characterized polypeptide composition.
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PMID:Purification of viral proteins from avian sarcoma virus QV2. 11 57

6-(P-hydroxyphenylazo)-uracil (HPUra) reduced by dithiothreitol inhibited AMV or RLV virion associated exogenous RNA-dependent DNA polymerase reactions. However, the inhibition was variable from experiment to experiment and was not consistent with the base specificity of HPUra seen for inhibition of gram positive DNA-dependent DNA polymerases. Increasing the concentration of dithiothreitol reversed the inhibition. Furthermore, at non-toxic concentrations, HPUra did not influence the plating efficiency of RLV in tissue culture, as measured by the ability to induce foci on sarcoma virus positive-leukemia virus negative cells. Oxidation of dithiothreitol in the presence or absence of HPUra was followed spectrophotometrically under enzyme conditions. HPUra catalyzed the oxidation of dithiothreitol under these conditions. Since dithiothreitol is required for optimum reaction rates, as well as complete disruption of virus in some polymerase assay systems, the oxidation of dithiothreitol in the presence of HPUra is sufficient to explain the inhibition seen.
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PMID:Inhibition of RNA-dependent DNA polymerase reaction by 6-(p-hydroxyphenylazo)-uracil: A result of drug induced dithiothreitol oxidation. 16 20

Non-producer (NP) human cells induced by the Kirsten sarcoma virus were characterized. These morphologically altered NP cells produced neither infectious virus nor complement-fixing antigens of the murine sarcoma-leukemia virus complex. The NP cells did not release RNA-dependent DNA polymerase and type-C virus particles with a density of approximately 1.15 g/ml in sucrose gradients by 3H-uridine labelling. The NP cells produced tumors when transplanted subcutaneously into athymic nude mice. The tumor cells re-established in culture resembled the orginal NP cells, were confirmed as human cells by karyological analysis and were also found to be "non-producer". The sarcoma virus genome in NP cells could be rescued not only by co-cultivation with "helper virus"-releasing cells but also by superinfection with helper type-C viruses. Murine (Rauscher, Ki-MuLV, AT-124 and two other xenotropic viruses), feline, RD-114 and Simian (woolly monkey and baboon) type-C viruses possessed the ability to rescue the sarcoma genome from NP cells but not AKR leukemia virus. In addition, the feline leukemia virus titer obtained by the rescuing technique in NP cells was the same as those obtained in feline embryo and NP cells by CF induction assay.
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PMID:Characterization of non-producer human cells induced by Kirsten sarcoma virus. 17 Dec 29

Radioactive DNA complementary to nucleotide sequences in Moloney murine sarcoma virus (MSV) and Moloney leukemia virus (M-MuLV) complex was made by the endogenous reverse transcriptase reaction. These virus stocks contained a threefold excess of MSV over M-MuLV as measured by biological assay. The complementary DNA was an accurate copy of the viral RNA in that 86% of 35S viral RNA hybridized with complementary (cDNA) DNA at a 1.5 to 1 cDNA-RNA molar ratio. The complementary DNA, of a 4-6S size, was fractionated by sequential absorptions with MulV and the feline leukemia virus pseudotype of MSV, [MSV(FeLV)] RNA. In this manner three sets of nucleotide sequences whichrepresent different portions of the MSV viral complex were obtained: a sarcoma virus-specific fraction (cDNAsarc) with sequences that had no homology to M-MuLV RNA but which hybridized to MSV (FeLV) RNA, a sarcoma-leukemia fraction (cDNA common) with sequences common to MSV as well as M-MuLV viral RNA, and a cDNAleuk representing those nucleotide sequences found only in M-MuLV. Hybridization of MSV-MuLV viral 35S RNA with a threefold molar excess of cDNA's revealed that approximately 20% was hybridized with cDNAsarc, whereas approximately 75% was hybridized with cDNAcommon. M-MuLV 35S RNA alone did not hybridize with cDNAsarc but did hybridize 40 and 50% with cDNAleuk and cDNAcommon, respectively. The cDNAsarc represents about 25% of the total MSV sequences, whereas the cDNAcommon represents the remainder of the MSV virus genome. Some cDNAcommon sequences were shared by two other sarcoma viruses and several distinctly different isolates of MulV. In contrast, the MSV "sarc" sequences had little or no homology with two other murine sarcoma virus isolates.
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PMID:Fractionation of DNA nucleotide transcripts from Moloney sarcoma virus and isolation of sarcoma virus-specific complementary DNA. 17 90

Bone-marrow cells from two leukemic children were co-cultivated with the leukemic children A 7573. In early passages, C-type oncornaviruses were released as detected by extracellular reverse transcriptase assay. Co-cultivation of the infected canine cells with the non-producing cell lines R-970-5 (human) or K-NRK (rat) both transformed by Kirsten mouse sarcoma virus (MSV) yielded a new pseudotype of MSV that could transform rat embryo, rabbit SIRC and human kidney cells but not mouse embryo cells. The focur formation could be inhibited by an antiserum to the simian sarcoma virus but not by a serum directed against murine leukemia virus. A cell line derived from a focus of transformed cells became a highe virus is related to the simian sarcoma virus. It is concluded that the leukemic bone-marrow cells produce a C-type oncornavirus that can serve as a helper virus to the defective MSV.
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PMID:Detection of human C-type "helper" viruses in human leukemic bone marrow with murine sarcoma virus-transformed human and rat non-producer cells. 18 71

Superinfection of chicken embryo fibroblasts transformed by the defective Bryan strain of Rous sarcoma virus (BH-RSV) with two different reticuloendotheliosis viruses (REVs), REV strain T (REV-T) or spleen necrosis virus (SNV), resulted in the production of infectious sarcoma virus pseudotypes. These pseudotypes were neutralized by antiserum prepared against SNV and were unable to infect chicken cells preinfected with either REV-T or SNV. These results suggest that defective BH-RSV is able to use the glycoprotein from REV to form infectious pseudotypes. On the other hand, neither REV-T nor SNV was able to supply a functional reverse transcriptase to the polymerase-negative mutant BH-RSValpha, nor was REV-T or SNV able to complement the defect in the internal protein gene of the temperature-sensitive avian sarcoma virus mutant NY45.
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PMID:Formation of reticuloendotheliosis virus pseudotypes of Rous sarcoma virus. 19 82

Simian sarcoma virus, type 1 (SSV-1)-transformed non-producer cell lines were established by infection of normal marmoset fibroblast cells (HF) with limiting dilutions of SSV-1. Four focus-derived cell lines were identified as non-producers by assay of culture fluids for focus-forming activity and by the mixed culture cytopathogenicity test with XC cells. Further studies failed to detect production of type-C virus by 3H-uridine labelling, reverse transcriptase assay or electron microscopy. The non-producer cell lines, designated HF/SSV-NPI, IV, V, and VI, appeared morphologically transformed and cloned in soft agar with the same efficiency as HF/SSV-1 virus-producing transformed cells. Expression of either cytoplasmic or cell surface virus-related antigens was not detected by immunofluorescence or serum cytotoxicity tests. The presence of sarcoma genome in the transformed non-producer cell lines was demonstrated by rescue of focus-forming activity following superinfection with non-transforming helper virus or by cocultivation with helper-virus-producing cell lines. The SSV-1-transformed non-producer primate cells provide a useful tool for future studies.
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PMID:Establishment of simian sarcoma virus, type 1 (SSV-1)-transformed non-producer marmoset cell lines. 19 78

We studied the transformation of epithelial, diploid cell lines (RL-33 and RL-34) derived from W rat liver by the Kirsten murine sarcoma virus. On days 4-5 after virus infection, the epithelial cells began to pile up focally, forming small projections and releasing round cells from the foci. The epithelial cells grew in chains or as islets and grew in suspension above the cells attached to the bottom of the flasks when the cultures reached the confluent stage. The virus titration pattern was "one-hit." Three classes of transformed cells were isolated with respect to virus release and antigen expression: 1) virus producer, 2) non-producer, and 3) sarcoma-positive, leukemia-negative cells. When transplanted sc into newborn rats, the transformed cells produced sarcomas. The transformed cells formed within 1-3 days larger aggregates than those of their normal counterpart cells when suspended in liquid growth medium above an agar base. Aggregate properties (size, viability, and proliferation) of transformed cells correlated with growth in soft agar and tumorigenicity. RNA-dependent DNA polymerase and type C virus particles were readily induced in the normal rat liver epithelial cells after exposure to 5-iodo-2'-deoxyuridine.
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PMID:Transformation of rat liver epithelial cells by Kirsten murine sarcoma virus. 19 67

Some morphological, biological, immunological and biochemical characterizations of a virus, rat helper virus pseudotype Kirsten sarcoma virus, KiMSV(RHHV), have been presented here. KiMSV(RHHV) has a type C virus ultrastructure. It is strictly rat tropic and is able to transform rat cells in vitro. The possibility of its being a xenotropic mouse virus has been carefully ruled out by exhaustive analyses of host range and immunological studies. Antigenically KiMSV(RHHV) demonstrates cross reactivity with an antiserum specific against rat leukaemia virus, no cross reactivity with antiserum against Moloney leukaemia virus, and only minor cross reactivity with antiserum against cat leukaemia virus. Analysis of virus proteins and glycoproteins by equilibrium acrylamide gradient gel electrophoresis showed that the virus complex possesses both a gp70 fraction and a p30 fraction. KiMSV(RHHV) sediments isopycnically in a linear sucrose gradient at 1.145 to 1.155 g/ml and possesses RNA and reverse transcriptase activity.
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PMID:Properties of a transforming virus, KiMSV(RHHV), isolated from a co-culture of rat HTC-H1 cells with K-NRK cells. 20 53


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