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)

Short-term cultures of bovine leukemic lymphocytes release virus particles with biochemical properties of RNA oncogenic viruses. These particles, tentatively called bovine leukemia virus (BLV), have a high molecular weight RNA-reverse transcriptase complex and a density of 1.155 g/ml in sucrose solutions. Molecular hybridizations between BLV/[3H]cDNA and several viral RNAs show that BLV is not related to Mason-Pfizer monkey virus, simian sarcoma associated virus, feline leukemia virus, or avian myeloblastosis virus. These results were confirmed by hybridization between BLV 70S RNA and [3H]cDNA synthesized in the various viruses tested. The high preference of BLV reverse transciptase for Mg++ as the divalent cation suggests that BLV might be an atypical mammalian leukemogenic "type C" virus. DNA-DNA hybridization studies using BLV [3H]cDNA as a probe strongly suggest that the DNA of bovine leukemic cells contains viral sequences that cannot be detected in normal bovine DNA.
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PMID:Bovine leukemia virus: an exogenous RNA oncogenic virus. 5 16

The cocultivation of spleen cells from the Southeast Asian mouse, Mus cervicolor, with heterologous cell lines has permitted the isolation of a new retravirus (designated M432) that can be transmitted to tissue culture cells of the laboratory mouse, M. musculus. Cells infected with M432 contain cytoplasmic type A particles and budding forms with compact,spherical nucleoids; extracellular virions lack surface spikes and have a condensed, central core surrounded by an intermediate line. Like other retraviruses, M432 bands isopycnically in sucrose at 1.16-1.17 g/cm3 and contains a 70S RNA genome composed of 35S subunits and an RNA-dependent DNA polymerase (RNA-dependent DNA nucleotidyltransferase). The viral reverse transcriptase requires magnesium as a cofactor and transcribes the synthetic template:primer poly(rC)-oligo(dG) more efficiently than poly(rA)-oligo(dT). [3H]DNA transcripts of the viral RNA genome detect multiple copies of endogenous virogene sequences in the cellular DNA of normal M. cervicolor, and fewer copies in heterologous cells infected with M432. Partially related nucleic acid sequences are also detected in the DNA of M. caroli and M. musculus as well as in more distantly related species (rat and hamster), reflecting the evolutionary conservation of these gene sequences in rodents. Although the virus from M. cervicolor shares certain morphologic and biochemical properties with murine type B viruses, the new isolate is unrelated by nucleic acid hybridization criteria to the mouse mammary tumor virus, the bovine leukemia virus, the Mason-Pfizer monkey virus, or known murine type C viruses, including endogenous type C viruses isolated from M. cervicolor.
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PMID:A new class of genetically transmitted retravirus isolated from Mus cervicolor. 6 62

Short term cultures of bovine leukemic lymphocytes release virus particles with biochemical properties of RNA oncogenic viruses. These particles, tentatively called Bovine Leukemia Virus (BLV) have a high molecular weight-reverse transcriptase complex and a density averaging 1.155 g/ml in sucrose solutions. Molecular hybridizations between BLV-3H cDNA and several viral RNAs show that BLV is not related to Mason-Pfizer Monkey Virus (MPMV) Simian Sarcoma Associated Virus (SSV-1) Feline Leukemia Virus (FeLV) or Avian Myeloblastosis Virus (AMV). Rauscher Leukemia Virus (RLV) exhibits a slight but reproducible relatednesse to BLV. The high preference of BLV reverse transcriptase for Mg++ as the divalent cation suggests that BLV might be an atypical mammalian leukemogenic type C virus. Hybridization studies using BLV 3H cDNA as a probe suggest that the DNA of bovine leukemic cells contains viral sequences that cannot be detected in normal bovine DNA.
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PMID:Bovine leukemia virus: an exogenous RNA oncogenic virus? 6 82

Sera from some leukemic cattle contain an antibody that inhibits the reverse transcriptase activity of the bovine leukemia virus. The antibody is not directed against the synthetic template or the major internal and envelope viral antigens. The antibody failed to inhibit the DNA polymerases of the murine leukemia virus, simian sarcoma-associated virus, avian myeloblastosis virus, or Escherichia coli. Conversely, the bovine leukemia virus enzyme was not inhibited by antibody against the reverse transcriptases of other C-type viruses. These findings agree with previous results showing that the major internal bovine leukemia virus protein lacks the known interspecies- and intraspecies-specific antigenic determinants indentified in the homologous proteins of other oncornaviruses.
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PMID:Inhibition of the reverse transcriptase of bovine leukemia virus by antibody in sera from leukemic cattle and immunological characterization of the enzyme. 6 83

A new retravirus (SMRV) isolated from a squirrel monkey, Saimiri sciureus, has an Mg2+-dependen reverse transcriptase and a buoyant density of 1.17 g/cm3 in sucrose and 1.21 g/cm3 in cesium chloride, similar to the mouse mammary tumor virus and the Mason-Pfizer monkey virus. The polypeptide patter of SMRV as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis was distinct from the reported polypeptide patterns of known retraviruses. Four major polypeptides of molecular weights 40,000, 20,000, 14,000 and 8,000 were resolved in virus propagated in human, mink, and canine cells. In A204 human rhabdomyosarcoma cells, a protein of 73,000 daltons (gp73) represented the major viral glycoprotein as determined by [3H]glucosamine labeling. Additional proteins were also observed, but their presence depended on the cell type in which the virus was propagated. In both species-and interspecies-specific assays, no antigenic relatedness was observed between SMRV and Mason-Pfizer monkey virus, mouse mammary tumor virus, baboon endogenous virus (BaLV), woolly monkey virus (SSV-1), murine leukemia virus, endogenous feline type C virus (RD-114), bovine leukemia virus, and equine infectious anemia virus. These findings indicate that SMRV represents a new retravirus and the first isolate from a New World monkey.
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PMID:Characterization of a retravirus isolated from squirrel monkeys. 6 28

An RNA-dependent DNA polymerase or reverse transcriptase has been demonstrated in highly purified bovine leukemia virus (BLV) particles. The viral enzyme responded very effectively to the exogenous template primer polyneucleotide (poly) (rA)-oligonucleotide (oligo) (dT). Unlike the reverse transcriptases of most mammalian C type RNA viruses, and of the ubliquitous foamy-like bovine syncytial virus, the BLV enzyme prefers magnesium rather than manganese for optimal activity. The identification of several other conditions required for optimal activity of the viral reverse transcriptase led to the development of a rapid, sensitive, semiquantitative assay, which is comparable in sensitivity to the syncytia-infectivity assay for the detection of BLV in supernatant fluids of monolayer cell cultures. However, the reverse transcriptase assay is not sufficiently reproducible for obtaining routine detection of BLV in short-term cultures of bovine peripheral blood lymphocytes. Therefore, this assay does not seem to provide an accurate method for the diagnosis of BL virus infection in cattle.
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PMID:A reverse transcriptase assay for detection of the bovine leukemia virus. 7 57

A method for the study of oncovirus envelope antigens was developed, bases on the precipitation of intact virions by a double antibody technique. The amount of precipitated virus was then measured as reverse transcriptase activity. The method was designated the virion precipitation test (VPT). It has been used for titration of antibodies to envelope antigens of oncoviruses. The study of envelop antigens of 11 different oncoviruses permitted their differentiation into the following groups: (1) murine type-C viruses: (2) feline type-C viruses; (3) simian type-C viruses; (4) the RD-114/BEV group; (5) Mason-Pfizer monkey virus (M-PMV); (6) bovine leukemia virus; (7) avian type-C viruses; (8) mouse mammary tumor virus. No common antigenic determinants were detected in the last three groups. Mammalian type-C viruses (RD-114, NIH-MuLV, G-MuLV) had common antigenic determinants in the envelope, as demonstrated with an anti-RD-114 serum. Mammalian type-C viruses also shared antigenic determinants with M-PMV. The relationship of type-C viruses to M-PMV decreased in the following order: RD-114--NIH-MuLV--G-MuLV. It was also shown that the endogenous xenotropic feline RD-114 virus was more closely related to xenotropic NIH-MuLV than to ecotropic G-MuLV. The nature of the common antigenic determinants, as demonstrated by VPT on the surface of mammalian type-C viruses and M-PMV, and their significance for the concept of oncovirus evolution are discussed.
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PMID:A new virion precipitation test for oncovirus envelope antigens which detects common antigenic determinants in mammalian type-C viruses and Mason-Pfizer monkey virus. 8 21

An RNA-directed DNA polymerase was purified from bovine leukemia virus (BLV) by successive glycerol gradient centrifugation, column chromatography on phosphocellulose and gel filtration on Sephadex G-200. The purified DNA polymerase transcribes heteropolymeric regions of 30--40 S RNA isolated from avian myeloblastosis virus. The enzyme differs from other known DNA polymerases of mammalian type-C RNA tumor viruses by the following properties: 1. Its apparent molecular weight as estimated by velocity sedimentation data is 58,000 at 0.12 M KCl and 43,000 in the presence of 0.50 M KCl. 2. It has a Mg2+ optimum of 10 mM, and a Mn2+ optimum of 0.25 mM with (rA)n-(dT)10 as template. 3. At 50 mM KCl it is inhibited more than 70%, but it is not inhibited by phosphate ions at 2 mM. These properties confirm the peculiar position of BLV within the family Retraviridae.
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PMID:Purification and characterization of bovine leukemia virus DNA polymerase. 23 43

The gene for bovine leukemia virus (BLV) reverse transcriptase was cloned in prokaryotic expression vector pUC8-2. After fusion of Escherichia coli lacZ gene to different parts of reverse transcriptase we detected expression of new proteins with molecular weights corresponding to the size of the hybrid genes. A coding region most probably responsible for about a hundred-fold decrease in expression of long fusion proteins has been identified. A few possible causes of this phenomenon were tested.
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PMID:Expression of chimeric proteins encoded by the fused BLV reverse transcriptase: beta-galactosidase in Escherichia coli. 128 72

Incubation of adherent cells derived from peripheral blood mononuclear cells of cattle naturally infected with bovine leukemia virus (BLV) led to the establishment of three, persistently infected, primary cell cultures. These cultures were obtained exclusively from animals exhibiting persistent lymphocytosis, and not from uninfected or infected, hematologically normal cattle. The cells contained monoclonally integrated, full length BLV provirus, indicating that each culture resulted from clonal expansion of a single cell. They expressed high levels of all BLV specific mRNAs and showed intracellular reactivity to antibodies directed to viral gag and env proteins. Viral particle morphogenesis was highly restricted as determined by low levels of reverse transcriptase activity in cell supernatants and the paucity of viral particles on the cell surface. Analysis of cellular antigenic determinants, using monoclonal antibodies to bovine leukocyte differentiation and major histocompatibility complex antigens, was inconclusive. Cytochemical, morphologic, and ultrastructural analyses were consistent with endothelial cells and they exhibited the distinctive functional capacity of endothelial cells derived from specialized postcapillary venules, which constitute sites of lymphocyte extravasation. These data suggest that infection of these endothelial cells may be involved in the development of persistent lymphocytosis in BLV-infected animals.
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PMID:Isolation of bovine leukemia virus infected endothelial cells from cattle with persistent lymphocytosis. 165 65


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