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)

A new DNA polymerase was partially purified from cell-free extracts of a continuous rat cell-line (XC). The XC cells had been transformed by the Prague strain of Rous sarcoma virus but did not produce infectious virus. The molecular weight of the DNA polymerase is 70,000, as estimated by glycerol gradient centrifugation and by Sephadex gel filtration. This enzyme can be distinguished from the other cellular DNA polymerases by its elution pattern on DNA-cellulose column chromatography, its molecular weight, and its primer-template specificity. The enzyme has some characteristics of the murine leukemia virus reverse transcriptase. It is partially inhibited by immunoglobulin G purified from rabbit antiserum prepared against Rauscher leukemia virus reverse transcriptase, but is not inhibited by IgG from rat antiserum prepared against avian myeloblastosis virus reverse transcriptase. However, the XC cell enzyme can be distinguished from the murine leukemia virus reverse transcriptase by its inefficiency in copying an oligo(dG)12-poly(rC)primer-template.
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PMID:Partial purification and characterization of DNA polymerases from a Rous sarcoma virus-transformed rat cell line. 17 Sep 87

The oncornaviruses share several biological, biochemical, and structural properties that distinguish them from other RNA viruses. Rous sarcoma virus, a representative of avian oncornaviruses, manifests two major functions: cell transformation and virus replication. Both functions are independent, and are expressed separately in defective viruses. The virus has a 60-70S RNA, composed of 35 S subunits. It appears that each subunit of viral RNA carries the same genetic information and, furthermore, that 10% of this information is coding for cell transformation. Without this 10% the virus can still replicate. The RNA genome is expressed when the virus penetrates a sensitive cell, provided the virus carries an active reverse transcriptase. Virus-transformed cells possess a DNA form of the viral genome. The viral DNA is infectious, and can lead, upon transfection of permissive cells, to the production of a new viral progeny. We have established that the minimum molecular weight of the viral DNA is 6 X 10(6) daltons, and that this DNA is covalently bound to the chromosomal DNA. Also by examining the frequency of transfection events in the DNA-treated cells we suggest that transfection is a single-hit phenomenon. It follows that viral DNA of 6 X 10(6) daltons carries all the genetic information to code for the virus production. It seems likely that the transfection mechanism giving rise to transforming viruses is different from that producing nontransforming segments. In general terms, the experimental data indicate that certain RNAs and DNAs could accomplish malignant transformation if they are able to penetrate into the cell and give rise to the DNA forms which could be integrated into the cellular genome.
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PMID:[DNA form of the genome of oncornaviruses]. 17 70

Analyses of the DNA polymerase present in the inner mitochondrial membrane and matrix fraction of the mitochondria isolated from Rous sarcoma cells and chick embryo cells, and in the lysate of Rous sarcoma virus were performed, using a modification of the thin-layer gel filtration on Sephadex G-150 superfine. The method allowed the simultaneous determination of the molecular weight of the isolated enzymes. In the mitochondria or Rous sarcoma cells an RNA-directed DNA polymerase, activated by poly(rA): oligo (dT) synthetic duplex, was detected, with the same molecular weight as the reverse transcriptase isolated from Rous sarcoma virus. Such enzyme was not found in the mitochondria of chick embryo cells.
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PMID:Detection of RNA-instructed DNA polymerase in the mitochondria of Rous sarcoma cells using sephadex G-150 thin-layer gel filtration. 17 3

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

The influence of 9-beta-D-arabinofuranosyladenine (ara-A) and its 5'-triphosphate derivative on programmed synthesis was tested with an intact cell system as well as with isolated enzyme systems. The effect of ara-A was tested in mouse lymphoma cells (L5178Y). The compound reduces cell proliferation in low concentration by cytostasis; under high ara-A concentration of radioactive precursors into DNA, RNA, and protein showed that ara-A selectively inhibits DNA synthesis. Formation of a polysome complex is not affected by ara-A. [3H]ara-A is incorporated into DNA in an intact cell system; 1 molecule of ara-A is incorporated per 8000 molecules of deoxyadenosine. Most of the ara-A molecules appeared to be in internucleotide linkages. Incorporation of ara-A into RNA could not be detected. 9-BETA-D-Arabinofuranosyladenine 5'-triphosphate (ara-ATP) does not reduce the incorporation rate of the following enzymes, isolated from quail oviducts: DNA-dependent RNA polymerases I and II, polyadenylic acid polymerase, and poly(adenosine diphosphate ribose) polymerase. The compound was found to inhibit DNA synthesis catalyzed by DNA polymerases isolated from quail oviducts and from oncogenic RNA viruses (Rous sarcoma viruses). All the enzymes tested were inhibited by ara-ATP in a competitive way with respect to deoxyadenosine 5'-triphosphate. The highest affinity of ara-ATP, i.e., the highest inhibitory potency of the drug, was found in the assays with the eukaryotic low-molecular DNA-dependent DNA polymerase. The influence on the eukaryotic high-molecular DNA-dependent Dna polymerase was a litte less. Compared to the eukaryotic DNA polymerases, the viral enzymes (RNA-directed DNA polymerase and DNA-directed DNA polymerase) are affected to a smaller extent by ara-ATP. No effects of ara-A and ara-ATP are observed in a protein-synthesizing, cell-free system isolated from L5178Y cells.
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PMID:Mode of action of 9-beta-D-arabinofuranosyladenine on the synthesis of DNA, RNA, and protein in vivo and in vitro. 114 31

The Rous sarcoma virus (RSV) integrase (IN) and the beta polypeptide (beta) of the reverse transcriptase are posttranslationally modified by phosphorylation on Ser at amino acid position 282 of IN. When IN was immunoprecipitated from RSV (Prague A strain) virions, approximately 30 to 40% of the IN molecules were phosphorylated. When IN was immunoprecipitated from a v-src deletion mutant (delta Mst-A) of RSV or from avian myeloblastosis virus (AMV), the percentage of IN molecules that were phosphorylated was significantly reduced. This reduction in phosphorylation of IN between virions was verified by [35S]Met-[35S]Cys or 32P labeling of IN, followed by immunoprecipitation analysis using antisera directed to the amino or carboxyl terminus of IN. In delta Mst-A or AMV, a nonphosphorylated, slightly truncated (at the carboxyl terminus) polypeptide was the major species of IN. The enhanced phosphorylation of IN does not appear to be a general function of transformed cells, since enhanced phosphorylation was not detected in AMV derived from viremic chickens or from a v-src deletion mutant of RSV propagated in a chemically transformed quail cell line, QT6. From these data, we conclude that v-Src is necessary for efficient phosphorylation of IN and beta.
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PMID:v-Src enhances phosphorylation at Ser-282 of the Rous sarcoma virus integrase. 131 16

Reverse transcription of the retroviral RNA genome begins with tRNA-primed synthesis of a minus-strand DNA, which subsequently acts as the template for the synthesis of plus-strand DNA. This plus-strand DNA is initiated at a unique location and makes use of a purine-rich RNA oligonucleotide derived by RNase H action on the viral RNA. To determine the variables that are relevant to successful specific initiation of plus-strand DNA synthesis, we have used nucleic acid sequences from the genome of Rous sarcoma virus along with three different sources of RNase H: avian myeloblastosis virus DNA polymerase, murine leukemia virus DNA polymerase, and the RNase H of Escherichia coli. Our findings include evidence that specificity is controlled not only by the nucleic acid sequences but also by the RNase H. For example, while the avian reverse transcriptase efficiently and specifically initiates on the sequences of the avian retrovirus, the murine reverse transcriptase initiates specifically but at a location 4 bases upstream of the correct site.
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PMID:Specificities involved in the initiation of retroviral plus-strand DNA. 168 26

Retroviruses encode proteinases necessary for the proteolytic processing of the viral gag and gag-pol precursor proteins. These enzymes have been shown to be structurally and functionally related to aspartyl proteinases such as pepsin and renin. Cerulenin is a naturally occurring antibiotic, commonly used as an inhibitor of fatty acid synthesis. Cerulenin has been observed to inhibit production of Rous sarcoma virus and murine leukaemia virus by infected cells, possibly by interfering with proteolytic processing of viral precursor proteins. We show here that cerulenin inhibits the action of the HIV-1 proteinase in vitro, using 3 substrates: a synthetic heptapeptide (SQNYPIV) which corresponds to the sequence at the HIV-1 gag p17/p24 junction, a bacterially expressed gag precursor, and purified 66 kDa reverse transcriptase. Inhibition of cleavage by HIV-1 proteinase required preincubation with cerulenin. Cerulenin also inactivates endothiapepsin, a well-characterised fungal aspartyl proteinase, suggesting that the action of cerulenin is a function of the common active site structure of the retroviral and aspartic proteinases. Molecular modelling suggests that cerulenin possesses several of the necessary structural features of an inhibitor of aspartyl proteinases and retroviral proteinases. Although cerulenin itself is cytotoxic and inappropriate for clinical use, it may provide leads for the rational design of inhibitors of the HIV proteinase which could have application in the chemotherapy of AIDS.
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PMID:In vitro inhibition of HIV-1 proteinase by cerulenin. 169 Jan 52

DNA polymerases have been isolated from muscle and melanoma tissues of Xiphophorus, which are similar to retroviral RNA-dependent DNA polymerases as they prefer RNA to DNA templates. They appear to associate with submicroscopic structures which exhibit a density of about 1.13 g/ml after sucrose-density-gradient centrifugation. The RNA-dependent-DNA-polymerase-like enzymes could be separated from the DNA-dependent DNA polymerases by DEAE-cellulose chromatography. Further purification on phosphocellulose revealed that the muscle enzyme eluted at the void volume and at about 0.6 M KCl, whereas most of the melanoma enzyme eluted at 0.1 M KCl. Comparison of the template primer specificities of the muscle and melanoma enzymes with those of known DNA polymerases showed obvious similarities to the RNA-dependent DNA polymerase isolated from Rous sarcoma virus.
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PMID:Detection of RNA-dependent DNA polymerase activity in the Xiphophorus melanoma system. 169 Jun 49

Alizarin complexone (AC), alizarin Red S (ARS) and various other anthraquinones were evaluated for their inhibitory effects on Rous-associated virus 2 reverse transcriptase (RAV-2 RT). Some 1,2-dihydroxyanthraquinones were active against this enzyme and AC was the most potent inhibitor among these compounds [50% inhibitory concentration (IC50): 3.8 micrograms/ml]. AC slightly inhibited Rous sarcoma virus RT (RSV RT) and human immunodeficiency virus type 1 RT (HIV-1 RT) (IC50: 100 micrograms/ml and 45 micrograms/ml, respectively). However, AC efficiently inhibited focus formation by Rous sarcoma virus (RSV) and cytopathogenicity of human immunodeficiency virus type 1 (HIV-1). Simultaneous administration of AC with RSV to newborn chickens also delayed tumor induction by RSV.
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PMID:Antiretroviral activities of anthraquinones and their inhibitory effects on reverse transcriptase. 171 88


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