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)

Primary cultures of African green monkey kidney and rabbit kidney as well as diploid cell lines WI-38 and DBS-FRhL-2 were examined for evidence of tumorigenicity and latent RNA tumor viruses. Cells inoculated into immunosuppressed newborn hamsters and rhesus monkeys were not tumorigenic. Cells treated with 2'-deoxy-5-iodouridine to induce the production of latent viruses were examined by electron microscopy, density gradient centrifugation, and the reverse transcriptase enzyme assay. No evidence was found for RNA tumor viruses by the biochemical or biophysical methods used. The results indicated that each type of mammalian cell currently used in the production of virus vaccines would be acceptable for these parameters of safety if similar control procedures were applied at the time the vaccines were manufactured.
J Natl Cancer Inst 1976 Oct
PMID:Safety of viral vaccine cell substrates: a reevaluation. 6 64

The degree of inhibition of mammalian DNA-dependent RNA polymerases I and II and Moloney leukemia virus RNA-dependent DNA polymerase by pyran copolymer was dependent on the concentration of the divalent cation cofactor in the reaction mixture. Inhibition was completely blocked by an excess of divalent cations. It was concluded that pyran inhibited these enzymes by complexing with the essential divalent cation cofactor.
J Natl Cancer Inst 1976 Dec
PMID:Role of divalent ion complex formation in pyran--inhibition of nucleic acid biosynthesis. 6 66

Hormonal regulation of mouse mammary tumor virus (MMTV) synthesis was studied in the CCL-51-SF cell subline derived from the Sykes' mammary tumor cell line CCL-51 and adapted to grow in semi-synthetic in vitro conditions. The virus was quantitated by measuring the supernatant reverse transcriptase activity in exogenous reaction using poly (rA)-oligo (dT) and poly (rC)-oligo (dG) as template/primers. The cells produced a low but significant amount of virus in the absence of any hormones and serum proteins. The synthetic glucocorticoid dexamethasone increased production considerably, up to 100-fold. Pretreatment of CCL-51-SF cells with serum or 5-bromodeoxyuridine, BrdUrd, partly reduced the stimulation by dexamethasone of MMTV production. Insulin and prolactin alone or in combination had no stimulating effect on spontaneous MMTV synthesis and cell growth. Prolactin, and more efficiently the prolactin-insulin combination, enhanced the MMTV production stumulated with dexamethasone. Insulin alone remained without effect. The polyamine spermidine, but not spermine, increased the MMTV production over the control by a factor of 2. Polyamines did not influence cell replication at the concentrations used.
Int J Cancer 1977 Feb 15
PMID:Mouse mammary tumor virus production stimulated by hormones and polyamines in cells grown in semi-synthetic in vitro conditions. 6 40

The Friend erythroleukemia cell line T3-C12, which produces Friend murine leukemia virus (F-MuLV) and can be induced to synthesize hemoglobin by dimethyl sulfoxide (DMSO), was monitored for viral RNA-dependent DNA polymerase reverse transcriptase (RT) activity. The amount of viral 60-70S RNA released from DMSO-treated cells was unaffected or increased compared to that from control cells, while RT activity from treated cells was decreased. Accordingly, the specific activity in F-MuLV from DMSO-treated cells expressed as RT/70S RNA was decreased to 8% of the control activity. The 5-bromo-2'-deoxyuridine added to cultures containing DMSO reversed the differentiation process, and the F-MuLV thus treated did not exhibit the reduced RT activity normally observed in DMSO-treated virus. Cell-free F-MuLV incubated with and without DMSO showed the same RT activity, indicating that DMSO itself did not inhibit RT activity. However, when F-MuLV-containing pellets from control and DMSO-treated culture fluids were mixed, there was marked inhibition of the control RT activity, suggesting that RNase hybrid activity was stimulated or that an inhibitor was produced. Assays of F-MuLV-RNase hybrid released from control and DMSO-treated cells showed no difference in activity, indicating that a specific inhibitor of RT was produced or activated. Additions of certain nucleotide triphosphates to RT incubation mixtures did not result in any stimulation of RT activity in DMSO-treated F-MuLV, suggesting that phosphatase was not responsible for the observed inhibition. The results suggested that DMSO treatment of T3-C12 cells caused a reduction in viral RT activity by stimulating the production of an inhibitor, the nature of which is unknown.
J Natl Cancer Inst 1977 Mar
PMID:Viral reverse transcriptase suppression associated with erythroid differentiation of Friend leukemia cells. 6 77

The properties of an RNA-dependent DNA polymerase, which occurs ubiquitously in the allantoic fluid of uninfected, leukosis-virus-free eggs, are described. It is shown that the enzyme can synthesize faithful transcripts from natural RNA (globin mRNA). With biochemical and immunological methods, the enzyme can be clearly distinguished from the reverse transcriptases of the known chicken RNA tumour viruses and therefore seems to be a member of a so far unknown class of chicken polymerases. Our data show that in the chicken system reverse transcriptase can occur without connection to the replication of RNA tumour viruses and without relationship to the induction of malignancy.
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PMID:Characterization of a new reverse transcriptase of possibly cellular origin in the chicken system. 6 20

Bleomycin inhibits cellular RNA synthesis and the inhibition is nonspecific. The ratio of polyadenylate- [poly(A)] containing RNA to non-poly(A)-containing RNA in the drug-treated human lymphocytic cells, line Wil2, was the same as that in untreated cells. Poly(A) RNA isolated from untreated cells was used as a template for reverse transcriptase to synthesize complementary DNA, which was then used as a probe to assay the sequence diversity of poly(A)RNA's from treated and untreated cells. It was found that essentially all of the poly(A) RNA's in the untreated cells were also present in the treated cells. The effect of bleomycin on the biological activity of messenger RNA (mRNA) was tested with globin mRNA in a wheat germ embryo translation system. Although bleomycin inhibited protein synthesis at high concentrations, the inhibition was not due to a modification of mRNA. This was evidenced by the fact that no decrease in the ability of mRNA to function in the test system was found when globin mRNA was pretreated with high concentrations of bleomycin followed by removal of the drug.
Cancer Res 1977 May
PMID:Effect of bleomycin on the synthesis and function of RNA. 6 80

Sera from some leukemic cattle contain an antibody that inhibits the reverse transcriptase activity of the bovine leukemia virus. The antibody is not directed against the synthetic template or the major internal and envelope viral antigens. The antibody failed to inhibit the DNA polymerases of the murine leukemia virus, simian sarcoma-associated virus, avian myeloblastosis virus, or Escherichia coli. Conversely, the bovine leukemia virus enzyme was not inhibited by antibody against the reverse transcriptases of other C-type viruses. These findings agree with previous results showing that the major internal bovine leukemia virus protein lacks the known interspecies- and intraspecies-specific antigenic determinants indentified in the homologous proteins of other oncornaviruses.
Cancer Res 1977 May
PMID:Inhibition of the reverse transcriptase of bovine leukemia virus by antibody in sera from leukemic cattle and immunological characterization of the enzyme. 6 83

Production of infectious Mason-Pfizer monkey virus (M-PMV) was enhanced after treatment of the CMMT cell line with 2.5 x 10(-5) M dexamethasone phosphate (DXM). The reverse transcriptase (RT) activity and infectivity titers of treated culture fluids were enhanced by five- and tenfold, respectively. Along with stimulation of M-PMV synthesis, a simian type C virus (SCV) was also detected by electron microscopic and RT analyses. The SCV was serologically related to the endogenous baboon type C virus. 5-iododeoxyuridine (IUDR) also activated the SCV in the CMMT cell line while significantly inhibiting the production of infectious M-PMV. The activation of endogenous SCV by IUDR or DXM was transitory, since removal of these compounds from the growth medium resulted in the disappearance of SCV buds and the related RT activity; however, low levels of specific viral structural proteins continued to be synthesized intracellularly. Similarly, the enhancement of M-PMV production seen with DXM was lost when the treated cells were subcultured for 2 weeks in the absence of the hormone.
J Natl Cancer Inst 1977 May
PMID:Expression of Mason-Pfizer and simian type C viruses in the presence of 5-iododeoxyuridine and dexamethasone. 6 14

The effect of busulfan therapy on the activity of oncornavirus-like particles and chromosome patterns in patients with polycythemia vera and essential thrombocythemia was studied. Three patients had pretreatment platelet counts greater than 1 million/microliter, abnormal bone marrow karyotypes, and electron microscopic and biochemical evidence of oncornavirus. The results demonstrated that in all 3 patients virus-like particles and reverse transcriptase-like activity could no longer be found in the platelets within 2-4 weeks after the initiation of busulfan treatment. The platelet count was still elevated at this point for each patient, although the count returned to normal levels within 2-3 weeks after virus-like activity was no longer detectable. The chromosome patterns, characterized by aneuploidy (30-50%) before treatment, improved after therapy.
J Natl Cancer Inst 1977 Jul
PMID:Effect of busulfan on oncornavirus-like activity in platelets and chromosomes in polycythemia vera and essential thrombocythemia. 6 34

Northern poke lymphosarcoma DNA polymerase was partially purified from particulate fractions banding at 1.15 to 1.16 g/ml from homogenates prepared from frozen necropsies of tumor-bearing pike. The enzyme behaves as a typical reverse transcriptase, in that it prefers ribotemplates to deoxytemplates. The isoelectric point (pl 5.5) is similar to that of avian myeloblastosis virus polymerase. The pike enzyme elutes from a phosphocellulose column at 0.22 M potassium phosphate, the same as avian myeloblastosis virus DNA polymerase. The enzyme activity is inhibited by pyran, a specific inhibitor of viral DNA polymerases. The most striking difference between the pike lymphoma polymerase and the other viral DNA polymerases tested is the low maximum temperature of 20 degrees, compared to 30 degrees for Rauscher leukemia virus polymerase and 38 degrees for avian myeloblastosis virus and Rous sarcoma virus.
Cancer Res 1977 Sep
PMID:Presence of DNA polymerase in lymphosarcoma in northern pike (Esox lucius). 6 92


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