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)

Virions produced by cells in the presence of actinomycin D (Act D virions) contain reverse transcriptase but are deficient in 70S genomic RNA. To assess the role of genomic RNA in encapsidation of a functional reverse transcriptase and to study the interaction of the enzyme and its template in the cores of intact virions, the reverse transcriptase enzymes of normal and Act D virions were compared. The enzymes were indistinguishable by column chromatography, sedimentation velocity, or template/primer preferences. In addition, these enzymes showed equal sensitivity to inactivation by antibodies directed against Rauscher murine leukemia virus DNA polymerase. The enzymes from Act D and normal virions had similar thermal decay rates and were both protected against heat denaturation by natural and synthetic template/primers. By these criteria, the DNA polymerase molecules synthesized and assembled into virions in the absence of genomic RNA are identical to those packaged under normal conditions. Additional studies designed to measure protection of reverse transcriptase by genomic RNA were carried out by comparing the thermal lability of the enzyme in intact Act D and normal virions. The thermal decay rate of reverse transcriptase in Act D virions was identical to that in control virions. In contrast to the lability of the virion-associated enzyme, however, genomic RNA in control virions was stable to heat treatment.
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PMID:Interactions of murine leukemia virus core components: characterization of reverse transcriptase packaged in the absence of 70S genomic RNA. 7 60

Poly (2-azaadenylic acid) [(aza2A)n] and poly(2-azainosinic acid [(aza2I)n], two newly synthesized analogues of (A)n and (I)n, in which CH-2 of the purine ring is replaced by a nitrogen atom, have been evaluated in various biological assay systems. (Aza2A) n formed a complex with (U)n and (br5U)n, and (aza2I)n formed a complex with (C)n and (br5C)n, but these complexes were markedly destabilized relative to the corresponding (A)n or (I)n complexes. The (aza2A)n-and (aza2I)n-derived complexes failed to stimulate the production of interferon in primary rabbit kidney cells and human diploid fibroblasts, under conditions (A)n. (U)n, (I)n. (C)n and (I)n. (br5C)n induced high amounts of interferon. both (aza2A)n and (aza2I)n exerted a marked inhibitory effect on the endogenous RNA directed DNA polymerase (reverse transcriptase) activity associated with murine leukemia virus. They caused a relatively mild inhibition of complement activity in an hemolytic assay system.
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PMID:Biologic activities of poly (2-azaadenylic acid) and poly (2-azainosinic acid). 7 66

Reverse transcriptase from foamy virus, strain H4188 was estimated and purified. The enzyme has the following characteristics: 1. The reaction utilized preferentially oligo (dT) poly (rA) as a primer-template; however, the synthetic primer-template oligo (dT) poly (dA) could also be used to some extent. 2. The reaction utilized oligo (dG) poly (rC) as a primer-template with very low efficiency. 3. The crude virus preparation had a detectable endogenous reaction using the four deoxyribonucleotides for DNA polymerization. 4. The cation requirement for the enzyme reaction was much more biased for Mn++ than for Mg++ ions. 5. The molecular weight of the partially-purified enzyme was estimated to be about 80,000. Aggregates of 240,000 daltons were also seen. The activity of this enzyme was not inhibited by antisera against the reverse transcriptases of various type C RNA viruses, namely, feline endogenous leukemia virus, RD 114, Woolly simian sarcoma virus (SSV-1) and avian myeloblastosis virus (AMV). Antiserum against Rauscher leukemia virus (RLV) enzyme was marginally active against foamy virus enzyme, perhaps indicating a slight cross-reaction. The biochemical characteristics of foamy virus reverse transcriptase seemed to be very close to those of the type C RNA viruses, but the immunological reaction proved that the foamy virus reverse transcriptase was distinct from the others.
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PMID:Reverse transcriptase of foamy virus. Purification of the enzymes and immunological identification. 7 44

Cells of the established MvlLu mink line spontaneously released a reverse transcriptase-containing virus after long-term passage in tissue culture. By molecular hybridization, DNA of normal mink cells was found to possess extensive nucleotide sequence homology with a reverse-transcription product of the viral genome, demonstrating that the new isolate was an endogenous virus of mink origin. The mink virus shared antigenic determinants with the major structural proteins of known mammalian type C viruses. Double-antibody competition radioimmunoassays were developed by utilizing the purified major structural protein, p30, of the mink endogenous virus. The virus was shown to possess antigenic determinants unique from those of other known mammalian type C viruses. It exhibited a higher degree of immunological cross-reactivity with endogenous rat type C and horizontally transmitted feline leukemia viruses than with other mammalian type C viruses tested. The finding that mink cells can remain nonvirus producing for many cell generations argues that there normally exists some cellular restriction to endogenous virus expression in this species.
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PMID:Isolation and characterization of an endogenous type C RNA virus of mink (Mv1Lu) cells. 7 20

The isolation and preliminary characterization of a new temperature-sensitive mutant of Moloney murine leukemia virus, designated ts7, are reported. The infectivity of ts7, determined by a focus-forming unit assay, was reduced at least 100-fold when the virus was assayed at the nonpermissive temperature (39 degrees C) as compared with assay at the permissive temperature (34 degrees C). However, several lines of evidence indicated that the diminution of ts7 titer at 39 degrees C is not due to its inability to form virus particles at that temperature. The supernatant from ts7-infected cells grown at 39 degrees C showed significant infectivity when assayed at 34 degrees C; only small reductions in reverse transcriptase activity and fusion ability were observed when compared with supernatant from 34 degrees C ts7-infected cultures. That particles are produced at the nonpermissive temperature was confirmed by transmission electron microscopy of the supernatant from ts7-infected cells at 39 degrees C and by transmission electron microscope observations of mature particles trapped in the intercellular spaces of pelleted thin cell section. A possible explanation for the productivity at 39 degrees C of particles that are infectious at 34 degrees C but not at 39 degrees C is that the virus is heat labile at the nonpermissive temperature. Consistent with this hypothesis is the extreme heat lability of virus harvested at 34 degrees C. Such virus, when incubated at 39 degrees C, has a half-life one-sixth that of identical virus incubated at 34 degrees C, or that of wild-type virus at either temperature.
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PMID:Preliminary characterization of a temperature-sensitive mutant of Moloney murine leukemia virus that produces particles at the restrictive temperature. 7 22

The present study describes the separation and purification of a reverse transcriptase and cellular DNA polymerases from the human spleen of a patient with myelofibrotic syndrome. The specific requirements with respect to bivalent cations and template-primers for DNA polymerase-alpha, DNA polymerase-beta and DNA polymerase-gamma, as well as for the reverse transcriptase, are reported. Sedimentation-velocity measurements of the purified enzymes gave values of 150000, 40000, 100000 and 70000 daltons for DNA polymerase-alpha DNA polymerase-beta, DNA polymerase-gamma and the reverse transcriptase respectively. Serological studies have shown that the reverse transcriptase from human spleen is not antigenically related to cellular DNA polymerase-alpha, -beta or -gamma, but is antigenically related to reverse transcriptase from simian sarcoma virus and gibbon-ape leukaemia virus.
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PMID:Purification, biochemical characterization and serological analysis of cellular deoxyribonucleic acid polymerases and a reverse transcriptase from spleen of a patient with myelofibrotic syndrome. 7 8

Ouabain markedly inhibited the growth of the mouse cell lines K3b and JLS-V9 and the production of murine leukaemia virus (MuLV) in them. The inhibition of MuLV production was abolished by exposing the cells to normal medium or by adding a high concentration (43 mM) of K+ ions to the ouabain-containing medium. MuLV production was reduced by ouabain more rapidly than host cell directed protein synthesis. After treatment of cells with ouabain (0.5 mM) for 7 h, extracellular reverse transcriptase reverse transcriptase activities were reduced by 87 to 92%. However, the intracellular level of polymerase activities remained almost unchanged (77 to 98% relative to the control). Mouse interferon inhibited the production of MuLV in K3b cells and this antiviral action was not blocked by 0.5 mM-ouabain.
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PMID:Suppression of murine leukaemia virus production by ouabain and interferon in mouse cells. 7 44

This article concerns the molecular mechanisms by which RNA tumor viruses, commonly called as oncornaviruses, transfer their genetic information from the genomic RNA (70 s RNA) of the virions to the cellular DNA, leading to neoplastic transformations. The article describes biochemical and serological properties of reverse transcriptase, its role in the life cycle of RNA tumor viruses and broader implications to molecular biology. In this connection, the authors report their own findings on the role of reverse transcriptase in a preleukemic disease, myelofibrosis. This enzyme, discovered in their laboratory, is antigenically closely related to reverse transcriptase of certain primate RNA tumor viruses, and of human leukemic cells. The article also describes the role of reverse transcriptase inhibitors in viral oncogenesis. Of particular interest, is the partially thiolated polycytidylic acid (MPC) which has been developed by the authors, and is known to have a very high binding affinity to the viral reverse transcriptase. The implication of these basic data on the clinical effectivity of MPC in human leukemia, documented in a few cases, has been discussed.
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PMID:[Molecular biological aspects of oncogenesis caused by RNA tumor viruses (author's transl)]. 7 88

beta-Lapachone is a naturally occuring compound that can be isolated from a number of tropical trees. It is shown to be a potent inhibitor of reverse transcriptase activity from both avian myeloblastosis virus and Rauscher murine leukaemia virus. In addition, it affects eukaryotic DNA-dependent DNA polymerase-alpha activity: 50% inhibition is reached in 60-min incubation time by about 8 micron beta-lapachone. Enzyme activity is inhibited irrespective of the purity of the enzyme used or of the amount or type of template/primer or substrate present. The inhibitory effect of the drug is only observed in the presence of dithiothreitol. The primary site of action of beta-lapachone appears to be the enzyme protein, as is also borne out by the specificity of its action. Eukaryotic DNA-dependent DNA polymerase-beta, prokaryotic DNA-dependent DNA polymerase I, several other nucleic acid polymerases and some completely unrelated enzymes are not affected. Reverse transcriptase and DNA-dependent DNA polymerase-alpha may be in someway related in possessing similarly exposed '--SH structures' in their active sites. beta-lapachone thus affords a novel means of studying such interrelationships and of further characterizing enzymes.
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PMID:beta-Lapachone, an inhibitor of oncornavirus reverse transcriptase and eukaryotic DNA polymerase-alpha. Inhibitory effect, thiol dependence and specificity. 7 23

The microsomal supernatant fraction obtained from a murine cell line chronically infected with and producing Rauscher leukemia virus (JLSV-10) was found to contain two forms of RNA-directed DNA polymerase (reverse transcriptase). The two enzyme forms, neither of which is detectable in uninfected cells (JLSV-9), were initially partially purified by poly(C)-agarose chromatography, and their separation was achieved by phosphocellulose chromatography. The enzyme form eluting first from phosphocellulose (0.3 M KCl), designated PC I, was found to be identical in all parameters tested to that form isolated directly from purified virions. The second enzyme peak, designated PC II, eluted from phosphocellulose at 0.5 M KCl and was not detectable in purified virions. The PC II enzyme has a molecular weight, determined by velocity sedimentation, of approximately 109,000, as compared with 70,000 for the PC I enzyme, and could not be further dissociated by exposure to high salt or nonionic detergent. Mixing purified virion or PC I DNA polymerase with uninfected cells followed by fractionation did not produce the PC II form, suggesting that it is neither an artifact of purification nor the result of fortuitous complexing of reverse transcriptase with normal cellular component(s). Both PC I and PC II enzyme forms appeared antigenically similar to virion DNA polymerase, demonstrated identical divalent cation requirements for various template-primers, and were capable of copying heteropolymeric regions of rabbit globin mRNA. However, kinetic studies of heat inactivation revealed that the PC II enzyme was far more heat labile than the PC I form, which appeared identical to the virion enzyme in this respect. Furthermore, whereas the PC I and virion-derived reverse transcriptase copied poly(C).(dG)12-18 most efficiently at a template-to-primer molar nucleotide ratio of 25:1, the PC II enzyme preferred a ratio of 5:1 for optimal rates of poly(dG) synthesis. Therefore, by these criteria, there appear to exist two intracellular forms of reverse transcriptase in the JLSV-10 Rauscher leukemia virus-producing murine cell line.
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PMID:Resolution and characterization of intracytoplasmic forms of reverse transcriptase from Rauscher leukemia virus-producing cells. 7 32


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