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)

A protein kinase associated with purified virions of avian myeloblastosis BAI strain A was partially purified by ion-exchange chromatography and gel filtration. The transfer of phosphate catalyzed by this enzyme required a divalent metal ion and ATP as phosphate donor. GTP could not be substituted for ATP, and the reaction was unaffected by either cyclic AMP or beef-heart protein-kinase inhibitor. Of the virus and nonvirus proteins tested as phosphate acceptors, only acidic proteins were phosphorylated. In particular, purified preparations of reverse transcriptase from avian myeloblastosis virus did not accept phosphate. The enzyme is a basic protein (pI = 9.3), and, on the basis of molecular sieving through Sephadex G-200 and velocity sedimentation on glycerol gradient, the protein kinase has a molecular weight of 45,000.
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PMID:Protein kinase from avian myeloblastosis virus. 2 25

The effect of glucocorticoids on activation and replication of leukemia virus in AKR mouse embryo cells was analyzed. The number of cells detected as positive by fluorescent antibody techniques as well as the virus production in cells chronically producing virus was doubled at optimal concentrations of glucocorticoids. The effect of the hormones in activated cells was found to be not on the process of activation per se but rather on synthesis of the viral components after activation has occurred. Intracellular reverse transcriptase levels were not changed by hormone treatment. The stimulation of virus synthesis by glucocorticoids requires binding of the steroid to a cytoplasmic receptor protein.
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PMID:Effect of glucocorticoids on activation of leukemia virus in AKR mouse embryo cells. 4 95

Previously, type C RNA tumor virus-related components have been described in blood leukocytes from patients with acute myelogenous leukemia. These components, for example, reverse transcriptase, have been shown to be most closely related to those from two oncogenic subhuman primate type C viruses (woolly monkey sarcoma virus and gibbon ape leukemia virus). Now, we report the continuous production of budding type C viruses with the same characteristic reverse transcriptase by three separate culturings of leukocytes from a single bleeding from a patient with acute myelogenous leukemia. These isolations were made possible by the discovery of a source of conditioned media which sustains exponential growth of human myelogenous leukemia cells in liquid suspension culture.
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PMID:Type C RNA tumor virus isolated from cultured human acute myelogenous leukemia cells. 4 23

The salient biologic and morphologic characteristics of RNA tumor (oncornavirus) virus are reviewed. The ultrastructure of replicating oncornaviruses is illustrated in detail. C-type particles wide spread in at least three orders of animals were sighted in human sarcomas and leukemias. One case, an infantile fibrosarcoma, is presented from our cases surveyed for the presence of C-type particles. Tissue cultures derived from this tumor contained viral particles and had an elevated reverse transcriptase activity associated with the presence of 70 S RNA. The particles were larger (125 to 150nm) than those of the murine or avian Type C particles.
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PMID:Search for C-type particles in human neoplasia. 4 42

Purified reverse transcriptase from avian myeloblastosis virus or Rous sarcoma virus consists of two subunits of average mol wt of 100,000 and 60,000. The lower-molecular-weight subunit, alpha, has been isolated from avian myeloblastosis virus, Rous sarcoma virus and a temperature-sensitive mutant of Rous sarcoma virus, LA337. Subunit alpha manifests both the DNA polymerase and RNase H activities associated with purified reverse transcriptase of avian RNA tumor viruses. The thermal inactivation of these enzymatic activities of alpha subunit from the wild-type virus. The results show that both DNA polymerase and RNase H activities associated with the alpha subunit of LA337 are five to seven times more thermolabile then the corresponding alpha subunit from the wild-type virus. It is concluded that (i) both the polymerase and nuclease activities reside on the same polypeptide chain, and (ii) at least the lower-molecular-weight subunit alpha is coded for by the viral RNA.
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PMID:Studies on reverse transcriptase of RNA tumor viruses. I. Localization of thermolabile DNA polymerase and RNase H activities on one polypeptide. 4 81

The RNA-dependent DNA polymerase present in intracisternal A-type particles from mouse myeloma tumor cells has been studied. This polymerase can use either endogenous A particle RNA or an exogenous synthetic polynucleotide [poly (rA)] as a template. The DNA reaction product is small (4S-10S) and over 90% of it hybridizes to A particle RNA, whereas up to 50% of it hybridizes to murine sarcoma-leukemia virus RNAs. The RNA isolated from purified A particles is generally of low molecular weight (5S-15S) but contains small amount of 70S and 35S components. These results suggest that A-type particles may be related to C-type oncornaviruses.
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PMID:Characterization of DNA polymerase and RNA associated with A-type particles from murine myeloma cells. 4 84

Simian sarcoma-associated virus type 1 propagated in human rhabdomyosarcoma cells exhibited characteristics typical of oncornaviruses but seemed to have several aberrant properties. It had a buoyant density of 1.14 g/cm3, had RNA-dependent DNA polymerase activity, seemed to be labile to high salt concentrations, and contained little 50 to 60S RNA but relatively large amounts of human ribosomal RNA. In addition to 50 to 60S RNA, purified virions contained smaller RNA molecules with sedimentation coefficients of 28 to 30S, 18 TO 20S, and 4 to 10S. Unlike the 50 to 60S RNA species, the smaller virion-associated RNAs lacked polyadenylic acid, and the 28 to 30S RNA had an average base composition similar to that of human ribosomal RNA. Upon heat denaturation, the native 50 to 60S RNA genome yielded polyadenylic acid-containing 28 to 30S subunits that degraded in to 18 to 20S molecules upon further heat treatment. The 50 to 60S viral RNA had a guanine plus cytosine content of 56%.
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PMID:RNA of simian sarcoma-associated virus type 1 produced in human tumor cells. 4 85

RNA-DNA covalent hybrids containing viral RNA have been isolated from nuclear fractions of Rous sarcoma virus-infected chicken embryo fibroblast cells shortly after virus infection. The formation of covalent hybrid structures depends upon a functional reverse transcriptase in vivo, since its appearance in cells is temperature dependent when infected with Rous sarcoma virus mutant LA335, which contains a temperature-sensitive reverse transcriptase.
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PMID:RNA-dependent DNA polymerase activity of RNA tumor viruses. V. Rous sarcoma virus single-stranded RNA-DNA covalent hybrids in infected chicken embryo fibroblast cells. 4 86

A new method for the analysis and purification of the RNA-directed DNA polymerase of RNA tumor viruses has been developed. This nucleic acid affinity chromatography system utilizes an immobilized oligo (dT) moiety annealed with poly (A). The alpha and alphabeta DNA polymerases of avain myeloblastosis virus bound effectively to poly (A) oligo (dT)-cellulose. Alpha DNA polymerase did not bind effectively to poly (A) oligo (dT)-cellulose, poly (A)-cellulose, or to cellulose. Alphabeta bound to oligo (dT)-cellulose and cellulose at the same extent (approximately 30%), indicating that this enzyme did not bind specifically to the oligo (DT) moiety only. However, alphabeta bound to poly (A)-cellulose two to three times better than to cellulose itself, showing that alphabeta could bind to poly (A) without a primer. Alphabeta DNA polymerase also bound to poly (C)-cellulose, whereas alpha did not. These data show that the alpha DNA polymerase is defective in binding to nucleic acids if the beta subunit is not present. Data is presented which demonstrates that the alphabeta DNA polymerase bound tighter to poly (A). oligo (DT)-cellulose and to calf thymus DNA-cellulose than the alpha DNA polymerase, suggesting that the beta subunit or, at least part of it is responsible for this tighter binding. In addition, alphabeta DNA polymerase is able to reversibly transcribe avian myeloblastosis virus 70S RNA approximately fivefold faster than alpha DNA polymerase in the presence of Mg2+ and equally efficient in the presence of Mn2+. alpha DNA polymerase transcribed 9S globin m RNA slightly better than alphabeta with either metal ion.
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PMID:Binding properties of avian myeloblastosis virus DNA polymerases to nucleic acid affinity columns. 4 87

Nonionic detergents stimulate purified RNA-directed DNA polymerase (reverse transcriptase) activity from various RNA tumor viruses ranging from avian to primate species. The stimulatory effect of the nonionic detergent is dependent on the type and amount of template-primer. The greatest stimulation is obtained when high concentrations of (dT)12-18-(rA)n or activated salmon sperm DNA are used as template-primers. Little stimulation is obtained with viral 70S RNA or with (dT)12-18- (dA)n. The detergent stimulation appears to be specific for viral reverse transcriptase since this effect is not observed with purified bacterial DNA polymerase or with three known mammalian cellular DNA polymerases. This finding may, therefore, be a useful additional criterion for distinguishing viral reverse transcriptase isolated from cells from other cellular DNA polymerases. Nonionic detergent also has a stabilizing effect on viral DNA polymerase against thermal inactivation. This stabilizing effect is further enhanced by the presence of template-primer.
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PMID:On the stimulation of viral DNA polymerase activity by nonionic detergent. 4 56


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