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 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

Two-stage synthesis of double-stranded DNA was performed using purified rat transferrin mRNA as a template, reverse transcriptase and DNA polymerase I. Double-stranded transcripts of transferrin mRNA were cloned as recombinant plasmid derivatives of pBR322. The insert length in these plasmids varied from 150 to 1500 bp. Clones carrying transferrin mRNA sequences were identified using colony hybridization and Southern blot hybridization with 32P-cDNA probe. Nick-translated DNAs from transformed clones hybridized with a single component of rat liver polysomal RNA that corresponded to transferrin mRNA in its molecular weight (0.86 MD). In hybridization selection cell-free translation test cloned plasmid DNAs hybridized specifically with rat liver poly(A) +RNA that programmed the cell-free synthesis of a polypeptide identical to pretransferrin in antigenic properties and molecular weight.
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PMID:[Cloning of double-stranded DNA--a transcript of rat transferrin mRNA]. 620 Jul 63

We have used in vitro mutagenesis to explore the functions of the gene products encoded by the pol gene of Moloney murine leukemia virus (M-MuLV). Deletions were constructed at a variety of positions in the gene, and the altered DNA copies of the viral genome were introduced into mouse cells by cotransformation. The mutants could be divided into two classes depending on the phenotype and map position of the deletion within the pol gene. Mutants with deletions mapping in the 5' portion of the gene were found to be completely deficient in reverse transcriptase activity. Mutants mapping in the 3' portion of the gene, however, assembled and released virions with normal levels of reverse transcriptase and RNAase H activities. When applied to permissive cells, these virions directed the synthesis of all three forms of unintegrated viral DNA: full-length, double-stranded linear DNA and the two circular forms with one and two copies of the long terminal repeat sequences. The infection was arrested at this point and the infected cells did not become producers of virus. Thus the 3' portion of the pol gene encodes a polypeptide with a function distinct from that of reverse transcriptase, which is not required for synthesis of viral DNA but is essential for establishment of that DNA in a stable, active form in the infected cell. We suggest that this function may be the integration of the proviral DNA.
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PMID:Construction and analysis of deletion mutations in the pol gene of Moloney murine leukemia virus: a new viral function required for productive infection. 620 67

A virus-specific ribonucleoprotein complex is present in the cytoplasm of reticuloendotheliosis virus-transformed chicken bone marrow cells. This ribonucleoprotein complex contains viral reverse transcriptase activity and may represent a precursor to the budding virion. The major viral polypeptide associated with the ribonucleoprotein complex was a polypeptide with a molecular weight of 63,000. This protein exhibited a precursor-product relationship with the major reticuloendotheliosis virus structural core protein p29. Core polypeptides were not associated with the intracellular ribonucleoprotein complex. Thus, p29 was incorporated into the virion in the form of its precursor Pr63. The cleavage of Pr63 in the ribonucleoprotein complex was accomplished either during the budding process of shortly after the release of particles from the cell.
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PMID:Assembly of avian reticuloendotheliosis virus: association of the core precursor polypeptide with the intracellular ribonucleoprotein complex. 624 76

We have examined in detail the major mRNA species encoded by the region of the herpes simplex virus type 1 genome encoded by HindIII fragment K (0.53-0.59 from the left end of the prototype arrangement of the genome) by using this restriction fragment bound to cellulose as a reagent for isolation of this mRNA. Before viral DNA replication in infected cells (early), a major species of viral mRNA 5.2 kilobases (kb) in length is abundant. After the onset of viral DNA replication (late), four mRNA species are abundant: 7, 5.2, 3.8, and 1.8 kb in size. We have used reverse transcriptase from avian myeloblastosis virus to make DNA complementary to these RNA species and their 3' ends. We have shown by hybridization of this complementary DNA to Southern blots of herpes simplex virus type 1 DNA that the 7-, 5.2-, and 1.8-kb mRNA species have their 3' ends to the right of 0.59 and are at least partially colinear. The 3.8-kb mRNA has a 3' end mapping to the left of the 3' ends of these other species. In vitro translation of HindIII fragment K-specific mRNA in a reticulocyte lysate system yielded three major polypeptide products: 140,000, 122,000, and 54,000 daltons (d). Less prominent species of 86,000 and 65,000 d also were produced. Translation of size-fractionated HindIII fragment K-specific mRNA showed that the 7-, 5.2-, and 3.8-kb mRNA's encoded the 54,000-, 140,000-, and 122,000-d polypeptides, respectively. The 140,000-d polypeptide was the major polypeptide translated using early HindIII fragment K-specific mRNA as a template. The 3.8-kb mRNA also encoded the 86,000-d polypeptide, whereas the 1.8-kb mRNA encoded a polypeptide that was indistinguishable from the 54,000-d polypeptide encoded by the 7-kb mRNA, in addition to the 65,000-d polypeptide. The implications of the data are discussed.
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PMID:Isolation and translation of mRNA encoded by a specific region of the herpes simplex virus type 1 genome. 625 Dec 46

Preparations of purified Rauscher murine leukemia virus were found to contain an endodeoxyribonuclease after disruption of the virus with nonionic detergents. The enzyme makes single-strand breaks in linear or covalently closed circular phage double-stranded DNA molecules. The enzyme was partially purified by ion-exchange chromatography on DEAE- and carboxymethyl-Sepharose columns followed by electrophoresis in DNA-containing polyacrylamide gels. The enzyme was separated from reverse transcriptase (p80pol), and the final endonuclease preparation contained no detectable reverse transcriptase activity. The DEAE-Sepharose column-purified endonuclease activity contained a polypeptide of about 40,000 Mr that we term p40. Peptide mapping experiments demonstrated that p40 shares methionine-labeled tryptic peptides with Pr200gag-pol and Pr135pol. Six major methionine-labeled tryptic peptides derived from p40 were found in Pr200gag-pol, but only five of these were detected in Pr135pol. The four core proteins (p30, p15, pp12, and p10) and p80pol plus p40 account for most, but not all, of the peptide sequences of Pr200gag-pol. The endonuclease-associated p40 is similar in size and precursor origin to the avian retrovirus-coded endonuclease (p32). In view of these similarities to the avian p32 endonuclease and its association with partially purified Rauscher murine leukemia virus-associated endonuclease preparations, we propose that p40 is the Rauscher murine leukemia virus-coded endonuclease.
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PMID:Endodeoxyribonuclease activity associated with Rauscher murine leukemia virus. 626 Sep 82

Avian myeloblastosis virus (AMV)-infected cells contain two viral mRNA's, a genome-sized 34S (7.5-kilobase) mRNA and a 21S (2.5-kilobase) subgenomic mRNA, which contains the AMV-specific sequences (myb sequences). We found that AMV virions packaged both the 7.5-kilobase full-length genomic RNA and the 2.5-kilobase subgenomic RNA. In vitro translation of AMV virion RNA sized by sucrose density gradient centrifugation yielded 76,000-, 56,000-, 48,500-, 47,000-, and 32,000-dalton products. The 76,000-dalton protein was coded for by RNA throughout the gradient, but the peak of activity was at 34S to 35S. The 56,000-, and 48,500-, and 32,000-dalton proteins were encoded in a 21S RNA, and 47,000-dalton protein was encoded in an RNA of approximately 24S. The 76,000-dalton protein was identified as Pr76gag, based upon immunoprecipitation with specific antiserum and the presence of the 19* dipeptide. 7-Methylguanosine triphosphate inhibited the syntheses of Pr76gag and the 56,000-, 48,500-, and 32,000-dalton proteins, but not the synthesis of the 47,000-dalton protein. The 56,000-, 48,500-, 47,000-, and 32,000-dalton proteins were not immunoprecipitated by anti-gag, anti-reverse transcriptase, or anti-gp85 antiserum. Two-dimensional peptide maps of the 56,000- and 48,500-dalton proteins indicated that they were unique. In vitro translational products of myeloblastosis-associated virus 1 were also analyzed to aid in the identification of the AMV myb gene product(s); the translational products analyzed included Pr76gag, p60env, and a 56,000-dalton polypeptide which apparently was not identical to the 56,000-dalton AMV translational product, as determined by two-dimensional peptide mapping. Our data indicated that one of these proteins (56,000, 48,500, or 32,000 daltons) may represent the product of the AMV myb gene and, therefore, the putative transforming protein(s) of AMV.
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PMID:In vitro translation of avian myeloblastosis virus RNA. 627 Mar 66

The synthesis and processing of B77 avian sarcoma virus RNA in infected chicken embryo fibroblasts was followed in the presence and absence of cycloleucine, a competitive inhibitor of the synthesis of S-adenosylmethionine and thus an inhibitor of RNA methylations. An increase in the steady-state levels of genome-length RNA and a decrease in the steady-state levels of subgenomic RNA molecules were obtained in the S-adenosylmethionine-depleted avian sarcoma virus-infected cells after 24 h of treatment with the inhibitor. The total number of virus-specific RNA molecules per cell, however, remained relatively constant under either condition. The production of newly synthesized virus-specific RNA in cycloleucine-treated and untreated cells infected with a transformation-defective strain of B77 avian sarcoma virus was followed as a function of [(3)H]uridine labeling time. The accumulation of radioactive genome-length 8.4-kilobase (kb) RNA continued in cycloleucine-treated cells, and virus particle production proceeded at normal rates as previously shown by incorporation of labeled nucleoside precursors or amino acids. In contrast, newly synthesized 3.5-kb subgenomic mRNA, the putative mRNA for the envelope protein precursor, failed to accumulate in the treated cells. The extent of the inhibition in the appearance of the radioactive 3.5-kb RNA was correlated with the extent of the inhibition of viral genomic and cellular mRNA methylations and was a function of the cycloleucine concentration. Under conditions in which the accumulation of 3.5-kb envelope protein mRNA was blocked by the cycloleucine treatment, there were significant increases in the rate of synthesis of the polypeptide products of the genome-length RNA, the precursors to the non-glycosylated gag proteins (Pr76(gag)), and the reverse transcriptase (Pr 180(gag pol)) relative to the rate of synthesis of the envelope protein precursor (gPr 92(env)). These results suggest that there is an S-adenosylmethionine requirement for the splicing, but not for the synthesis, packaging, or messenger function, of avian retrovirus genome-length RNA. Possible reasons for this requirement are discussed.
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PMID:Accumulation of spliced avian retrovirus mRNA is inhibited in S-adenosylmethionine-depleted chicken embryo fibroblasts. 628 5

We have constructed recombinant DNA clones containing small complementary DNA (cDNA) sequences homologous to portions of a 4.8-kb yeast viral double-stranded RNA (dsRNA) (L1) that codes for the viral capsid polypeptide. Neither the viral dsRNA nor its in vitro transcript is polyadenylated; hence the cDNAs were synthesized by reverse transcriptase on the in vitro mRNA transcript made by the viral transcriptase, using sheared salmon sperm DNA as a random primer. This is the first reported cloning of cDNA homologous to a viral double-stranded RNA. This method should be of general utility for dsRNA viruses, since all have a capsid-associated transcriptase activity. The lengths of the overlapping cDNA inserts varied from 100 to 800 bp. About 40% of them mapped to the 5' end of the in vitro transcript, and these have been ordered. At least 1485 bp of this end of L1 is represented in the cloned cDNAs characterized. Using the cloned cDNAs as probes, we have shown that the L dsRNAs of two viral subtypes are similar at the transcription initiation site and dissimilar elsewhere.
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PMID:Cloning of cDNA to a yeast viral double-stranded RNA and comparison of three viral RNAs. 675 56

The molecular mechanisms that underlie ethanol dependence appear to involve alterations in GABAA receptor function and gene expression. In rat cerebral cortex, chronic exposure to ethanol alters many functional properties of GABAA receptors, including reduction of GABAA receptor-mediated chloride uptake. These functional alterations occur without a concomitant alteration in total receptor density or affinity. Previous investigations have shown that chronic ethanol exposure elicits alterations in mRNA and polypeptide levels for several abundant GABAA receptor subunits. For example, alpha 1 and alpha 2 subunit mRNA and polypeptide levels have been shown to decrease with chronic ethanol exposure. The present study was undertaken to further investigate the effects of chronic ethanol consumption on GABAA receptor subunit mRNA levels in rat cerebral cortex by using a competitive, quantitative reverse transcriptase-polymerase chain reaction assay that incorporates subunit-specific internal standards and allows for the absolute quantification of mRNA levels. We find that chronic ethanol consumption elicits a significant increase in alpha 4 subunit mRNA levels that is equal, in absolute amount, to a decrease in alpha 1 subunit mRNA levels. There is a small (30%) increase in gamma 2S but not gamma 2L subunit mRNA levels after chronic ethanol consumption. In addition, gamma 1 subunit mRNA levels are increased by 70%, whereas alpha 5, beta 1, beta 2, beta 3, gamma 3, and delta subunit mRNA levels do not change. We also reproduced results obtained previously by Northern blot analysis showing a 40% reduction in alpha 1 mRNA levels with no change in beta 2 subunit mRNA levels after chronic ethanol consumption. These results are consistent with the hypothesis that chronic ethanol consumption alters the function of GABAA receptors by eliciting changes in receptor subunit assembly. These changes may underlie the development of ethanol dependence.
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PMID:Chronic ethanol consumption differentially alters the expression of gamma-aminobutyric acidA receptor subunit mRNAs in rat cerebral cortex: competitive, quantitative reverse transcriptase-polymerase chain reaction analysis. 747 17


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