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 cDNA library of the polyA+ RNA from Prague B strain of RSV infected cells was constructed by the use of oligo(dT) primer and the reverse transcription method. The clones containing the LTR sequences were studied. The DNA sequences of several clones were studied and compared with the cDNA sequence of the long terminal repeat (LTR) region of a PrB strain of Rous sarcoma virus (RSV) which had previously been determined. By the analyses of several different cDNA clones, mutations were detected in the R region as well as in the U3 region of the LTR in two different cDNA clones. By comparing the DNA sequences of these cDNA clones with the original viral LTR, the error-prone hypothesis of the RSV reverse transcriptase was confirmed.
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PMID:cDNA sequence of the long terminal repeat of a PrB strain of the Rous sarcoma virus. 255 23

Monoclonal antibodies were developed that are specific for Rous sarcoma virus structural, polymerase (reverse transcriptase) and transforming proteins. The monoclonal antibodies were shown to bind to purified virus proteins in an indirect 125I-labelled Protein A binding assay suitable for screening even very large numbers of hybridomas. Additional tests for specificity included radioimmunoprecipitation of purified virus structural proteins P12 and P27, of reverse transcriptase subunits alpha and beta, and of the transforming protein pp60v-src. Pilot immunofluorescence and protein kinase assays of the expression of virus proteins in avian and mammalian cells infected by wild-type virus as well as by temperature-sensitive, transformation-defective virus mutants revealed that synthesis of virus structural and transforming proteins is hardly affected by changes in temperature, whereas the pp60v-src-associated kinase activity is temperature-sensitive in cells infected by most, but not all the virus mutants.
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PMID:Isolation of monoclonal antibodies specific for Rous sarcoma virus structural, polymerase and transforming proteins and their use for the study of mutant virus-infected cells. 258 50

The DNA sequence of the gag and pol regions of a provirus cloned from a bovine tumor is presented. In order to confirm these results the sequence of portions of a second clone, derived from a virus-producing cell line, was also determined. The gag gene was found to consist of 1179 nucleotides, which probably encode only three proteins: an N-terminal protein of 109 amino acids, a major core protein (p24) of 215 amino acids, and a nucleic acid binding protein (p12) of 69 residues. An open reading frame, whose translated product showed clear homology to the avian and murine proteases, was found beginning immediately upstream of the 3' end of gag. Following this protease region, a third long open reading frame, encoding 852 amino acids, showed clear homology to both avian and murine pol genes. The mechanism of translation of the protease and pol gene products cannot be predicted with certainty. Like Moloney murine leukemia virus (M-MuLV), BLV has a termination signal at the 3' end of gag, but unlike M-MuLV the protease is in a different reading frame. Like Rous sarcoma virus (RSV), BLV has a termination signal at the 3' end of the protease region and the reverse transcriptase is in a different (i.e., the third) reading frame. Possible translation mechanisms are discussed. Finally, the BLV gag and pol gene products are highly related to those of the human T-cell leukemia virus (HTLV); relatedness varied from 37% amino acid identities within the N terminal gag protein to 54% within the nucleic acid binding protein. Highly significant homology with both murine and avian type-C proteins was found within p24, p12, and the putative protease, reverse transcriptase, and endonuclease. Based on this homology, the BLV-HTLV family of viruses appears about equally distantly related to murine and avian type-C viruses.
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PMID:The gag and pol genes of bovine leukemia virus: nucleotide sequence and analysis. 299 90

Chicken embryo cells normally contain, in addition to deoxyribonucleic acid (DNA)-dependent DNA (D-DNA) polymerases, a novel "R-DNA-polymerase" which specifically copies polyriboadenylic acid strands. This R-DNA polymerase cannot copy natural ribonucleic acid or polyribocytidylic acid strands to a significant extent. Infection of cells with the leukovirus RAV-2 leads to the intracellular formation of large amounts of the viral RNA-dependent DNA polymerase whose properties differ from the cell R-DNA polymerase. Chicken cells transformed by a Rous sarcoma virus mutant which produce noninfectious alpha-type Rous sarcoma virus (f), a leukovirus known to be deficient in the viral RNA-dependent DNA polymerase, do not contain detectable viral RNA-dependent DNA polymerase, whereas the cellular R-DNA polymerase is found in normal amounts. There seems to be no relationship between the cellular R-DNA polymerase and the RNA-dependent DNA polymerase of the avian leukoviruses.
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PMID:Deoxyribonucleic acid polymerase activities in normal and leukovirus-infected chicken embryo cells. 411 36

Incubation of rat cells transformed by Rous sarcoma virus (RSV) in an arginine-deficient medium resulted in accumulation of particles in the culture medium. Such particles did not appear when the transformed rat cells were incubated in a complete medium nor in the medium of primary rat cells which were incubated either in arginine-deficient or complete media. The particles which were released from the arginine-deprived transformed rat cells resemble C-type particles in their properties. These particles band in sucrose gradients at a density of 1.16 g/ml and contain 35S ribonucleic acid (RNA) molecules and a reverse transcriptase activity. Analysis of the cytoplasm of transformed and primary rat cells, deprived and undeprived of arginine, revealed the presence of reverse transcriptase-containing particles which banded in sucrose gradients at a density of 1.14 g/ml. These particles differed from the particles released into the medium by the arginine-deprived RSV-transformed rat cells. The deoxyribonucleic acid (DNA) molecules synthesized in vitro by the reverse transcriptase present in the particles isolated from the medium of arginine-deprived cells hybridized to RSV RNA, whereas the DNA synthesized by the cell-bound enzyme had no homology to RSV RNA.
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PMID:Reverse transcriptase-containing particles induced in rous sarcoma virus-transformed rat cells by arginine deprivation. 411 37

The RNA-dependent DNA polymerase of Rous sarcoma virus is inhibited by N-methyl isatin beta-thiosemicarbazone and by thiosemicarbazide, but not by semicarbazide. These inhibitors also inactivate, upon contact with the virion, the transforming ability of Rous sarcoma virus. Sulfhydryl donors, such as 2-mercapto-ethanol, can prevent these effects. The RNA-directed activity of the purified polymerase is inhibited to a greater degree than is the DNA-directed activity. Two cations, Cu(++) and Hg(++), can inhibit RNA-dependent DNA polymerase and inactivate the transforming ability of the virus. Synergism between N-methyl isatin beta-thiosemicarbazone and Cu(++) occurs, since treatment of the virus with a low dose of either N-methyl isatin beta-thiosemicarbazone or Cu(++) has little effect; however, when the two compounds are mixed together, significant inactivation occurs. This observation supports the hypothesis that the antiviral action of thiosemicarbazones is a function of their ability to act as a ligand for metallic ions. Several cations (Ag(+), Co(++), Zn(++), Cd(++), and Ni(++)) significantly inactivate the RNA-dependent DNA polymerase, but have little effect on the transforming ability. In view of this result, the conclusion that the enzyme activity is required for transformation remains open to question.
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PMID:Inhibition of RNA-dependent DNA polymerase of Rous sarcoma virus by thiosemicarbazones and several cations. 411 22

The enzymatic transcription of DNA from the 70S RNA of Rous sarcoma virus (RSV) is initiated on the 3' terminus of a molecule of 4S RNA which is hydrogen bonded to the viral genome. We labeled this primer with radioactive deoxynucleotides, and demonstrated that its release from 70S RNA by thermal denaturation was accompanied by a reduction in the template activity of the viral RNA. Two-dimensional electrophoresis in polyacrylamide gels separated the 4S RNAs associated with the 70S RNA of RSV into approximately eight fractions, each of which appeared to contain a discrete species of tRNA. The RNA in one of these fractions served as the principal primer for initiation of DNA synthesis by both detergent-disrupted virions of RSV and purified RNA-directed DNA polymerase with RSV 70S RNA as template.
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PMID:Transcription of DNA from the 70S RNA of Rous sarcoma virus. I. Identification of a specific 4S RNA which serves as primer. 413 19

The 70S RNA of Rous sarcoma virus contains 4S RNAs which serve as primers for the initiation of DNA synthesis in vitro by the RNA-directed DNA polymerase of the virus. We purified these primers in three different ways-by isolation of the covalent complex between primer and nascent DNA, by differential melting of the 70S RNA, and by two-dimensional electrophoresis in polyacrylamide gels. The 4S RNAs purified by these procedures were homogeneous and possessed very similar if not identical nucleotide compositions and sequences. The RNAs were approximately 75 nucleotides long, had pG at the 5' terminus and CpCpA(OH) at the 3' terminus, and contained a number of minor nucleotides characteristic of tRNA. In contrast to most tRNA's, the primer lacked rTp and contained Gp (Psip, Psip, Cp) Gp (possibly in place of the characteristic sequence GprTpPsipCpGp). At least 50% of the 4S primers available on 70S RNA were utilized in a standard polymerase reaction in vitro.
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PMID:Transcription of DNA from the 70S RNA of Rous sarcoma virus. II. Structure of a 4S RNA primer. 413 20

The structural relationship of the small (alpha) and large (beta) subunits of reverse transcriptase isolated from two avian RNA tumor viruses has been examined by tryptic peptide analysis. Comparison of the tryptic hydrolysates of the isolated subunits by two-dimensional separation on thin-layer cellulose plates indicates that (i) the alpha subunit of reverse transcriptase of avian myeloblastosis virus is structurally related to the beta subunit; (ii) the alpha and beta subunits of the enzyme of Rous sarcoma virus also appear to be related; and (iii) there appears to be an extensive amino-acid sequence homology between reverse transcriptases of avian myeloblastosis virus and Rous sarcoma virus. Evidence is also presented that both alpha and beta subunits can be identified in purified avian myeloblastosis virions.
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PMID:Studies on the reverse transcriptase of RNA tumor viruses. Structural relatedness of two subunits of avian RNA tumor viruses. 414 May 14

The DNA polymerase of the Prague strain of Rous sarcoma virus of subgroup C and of the Schmidt-Ruppin strain of subgroup A has been solubilized. DNA polymerase purified by sucrose gradient sedimentation and chromatography on DEAE-cellulose represented less than 2% of the soluble [(14)C]protein of the virus. The enzyme was separated from 90% of the viral glycoprotein; it is probably different from the viral group-specific antigen. The sedimentation coefficient (s(20, w)) of the soluble DNA polymerase was 8 S before, and 6 S after, incubation with pancreatic RNase. The molecular weight of the 8S DNA polymerase was estimated to be about 170,000, and that of the 6S DNA polymerase to be about 110,000. Purified DNA polymerase had a high activity with 60-70S viral RNA or salmon DNA as template, but it had a low activity with heat-dissociated 60-70S RNA, influenza virus RNA, or the RNA of tobacco mosaic virus as template. Neither the 8S nor the 6S DNA polymerase had endogenous template activity. The DNA-dependent and the RNA-dependent DNA polymerase activities of the Prague strain coincided in sucrose gradients, both in the 8S and the 6S form. It is concluded that the RNA-dependent and the DNA-dependent DNA polymerase activities of the avian tumor viruses are probably due to the same enzyme.
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PMID:Properties of a soluble DNA polymerase isolated from Rous sarcoma virus. 432 88


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