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 significantly higher MuLV expression was demonstrated in cells of MNU-induced leukemia of mice compared to corresponding cells of untreated control animals by reverse transcriptase activity and XC cell assay. These positive findings were verified by determination of indirect immunofluorescence test to look for intracytoplasmic MuLV p30. The problem is discussed whether these viruses play a role in chemical leukemogenesis.
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PMID:Demonstration of C-type viruses in N-methyl-N-nitroso urea (MNU)-induced leukemia of mice by reverse transcriptase activity and XC assay. 615 22

The properties of the virus synthesized by each of three morphologically different cell lines originating from DBA/2J fetal liver cells transformed by the anemic strain of Friend leukemia virus in vitro were analyzed. The cells of line G-1 are malignant in syngeneic DBA/2 mice, grow in suspension, and are erythroid in origin. Cells of lines G-2 and G-3 are adherent, are epithelial in appearance, and produce no tumors in DBA/2J mice. Higher reverse transcriptase activity was detected in the culture fluid of lines G-2 and G-3, although virus from G-1 cells was more leukemogenic. Differences were also found in the virion density and size of the viral genome. RNA from the virions produced by G-2 and G-3 cells sedimented at 75 S in a sucrose gradient; virion RNA from G-1 cells sedmiented at 60 S. However, when subjected to polyacrylamide gel electrophoresis, all three virus strains showed identical RNA subunits with an estimated molecular weight of 2.6 X 10(6). Analysis of virion proteins by slab gel electrophoresis showed differences in envelope protein (gp71) components but not in the major core protein (p30). The properties of these viruses are stable and remain unchanged after passage in 3T3 cells.
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PMID:Variations in properties of virus released from morphologically different cell lines transformed in vitro by Friend leukemia virus. 616 May 80

The virus proteins, reverse transcriptase (RT) and p30, were found to increase with time in the subcellular fractions of lymphocytic tissue from either the thymus or spleen of AKR mice with spontaneous lymphocytic leukaemia. Significant levels of RT activity were first detected in the microsomal fractions of the two tissues at 15 and 20 weeks old, respectively. Although low amounts of p30 could be found in both tissues within the first week of life, the overall increase in the amount of p30 within each tissue followed much the same course as that shown by RT. In addition, a protein complex consisting of p30 and RT was first found in thymus and spleen lymphocytes of 15 and 20 week-old animals, respectively. The complex increased in amount in both organs as the animals aged, reaching a maximum level in 30 week-old mice. Repeated attempts to detect other virus proteins such as gp70 in association with the complex by immunological means were unsuccessful. The complex could not be found in lymphocytic tissue taken from younger animals or in 'non-target' organs, such as liver or kidney, of animals with leukaemia. In animals treated with antiviral IgG, which delayed the development of spontaneous leukaemia, the complex did not appear until much later in life (45 weeks) and then in considerably smaller amounts.
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PMID:Existence of a reverse transcriptase-p30 complex in AKR mice with a high incidence of spontaneous lymphocytic leukaemia. 616 45

The effect of high doses of poly(I).poly(C) induced mouse L-cell interferon on the development of Rauscher murine leukemia virus (R-MuLV)-induced erythroleukemia in BALB/c mice was determined. Female mice, 4 to 5 weeks old, were infected with R-MuLV and treated with interferon every 24 h starting 6 h after virus inoculation. Under these conditions injection of 3-5 X 10(4) units of interferon caused a partial inhibition of the leukemia process. Daily application of 3 X 10(5) units completely or almost completely inhibited the erythroleukemia. After 14 days of treatment with these high doses of interferon, spleen weights of interferon-treated infected mice were comparable to those of uninfected animals which received only interferon. Also, no Rauscher cells in spleens and livers of R-MuLV-infected interferon-treated infected animals could be demonstrated and the spleen structure was well preserved in these mice. In interferon-treated infected animals no virus could be detected in the serum as judged from the absence of reverse transcriptase activity in the serum. Moreover, no virus-infected cells could be demonstrated in spleen or liver as deduced from negative immunofluorescence data using anti-p30 and anti-gp70 sera. No virions budding from spleen cell membranes were seen by electron microscopic studies. However, when interferon treatment was stopped the leukemic process was reactivated and all the mice died. In control experiments interferon caused an inhibition of red blood cell formation and a 50 to 100% enlargement of the spleen. Pharmacokinetic data showed that, after intraperitoneal inoculation, maximum amounts of interferon were present in the peripheral blood after 1-2 h. After 12-24 h almost all interferon activity had disappeared from the blood.
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PMID:The effect of high doses of poly(I).poly(C) induced mouse L cell interferon on Rauscher leukemia virus induced erythroleukemia in BALB/c mice. 616 93

The effect of enucleation of synthesis of Moloney leukemia virus was studied in chronically infected YACIR-A9 mouse hybrid cells. The synthesis of infectious virus decreased gradually until, 12 h after enucleation, virtually no infectious virus was produced. As determined by particle-bound p30 and reverse transcriptase, cytoplasts produced a low level of noninfectious viral particles. Thus, the assembly of virus particles does not appear to be wholly dependent on the presence of the cell nucleus. In contrast, production of infectious particles shows an absolute requirement for the cell nucleus.
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PMID:Decay of Moloney leukemia virus production after enucleation of chronically infected mouse cells. 616 84

Model systems to study restricted primate retrovirus expression were established by de novo infection of canine foetal thymus cells (CF-2Th) and superinfection of HEL-12 cells with HEL-12 virus. In the resulting CF-2Th/HEL-12V cells and HEL-12/HEL-12V cells, four sequential stages of virus infection were defined by the production of reverse transcriptase (RT)-containing particles and expression of virus antigens as detected by radioimmunoassays. Stage 1 cells did not synthesize virus antigens or produce RT-containing particles. Stage 2 cells synthesized virus antigen but not RT-containing particles. Stage 3 cells synthesized antigen and produced RT-containing particles, and stage 4 cells synthesized virus antigens but no longer produced RT-containing particles. The duration of the four stage infection is 2 to 3 weeks in both cell types. Monospecific competition radioimmunoassays to detect HEL-12V p30 or gp70 antigen showed high levels of virus antigen throughout stages 2 to 4 of infection. Analysis of immunoprecipitates formed under conditions to detect either p30- or or gp70-containing proteins in cells pulsed and pulsed--chased with [3H]leucine showed the same spectrum of virus precursor polyproteins, intermediates and mature virion components in stage 2 to 4 cells in canine and human infections. Spent culture fluids collected from stage 3 and stage 4 CF-2Th/HEL-12V cells failed to reveal inhibitors of RT activity. Stage 4 CF-2Th/HEL-12V or HEL-12/HEL-12V cells labelled with [3H]uridine produced virions which incorporated [3H]uridine but did not have RT activity, suggesting that restricted infection is characterized by production of HEL-12V defective in RT activity.
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PMID:Restricted HEL-12 virus infections in de novo infected human and canine cells. 617 57

We studied a patient with a Philadelphia chromosome-positive chronic myeloid leukemia, who died in relapse after multiple transfusions and grafting with bone marrow from his monozygotic twin brother (referred to as "donor" in this paper). We present data indicating that this patient may have had a retro-virus infection that this virus is related to the group of exogenous primate type C retroviruses. Antibodies to simian sarcoma virus (SSV) M.W. 30,000 protein (p30) but not endogenous feline virus RD-114 could be found in patient but not donor serum. Patient but not donor cells were able to actively synthesize a p30 protein that could be precipitated with patient serum and rabbit anti-SSV p30 but not with donor serum or rabbit anti-RD 114 p30. Patient p30 resembles SSV p30 but not RD-114 p30 in peptide mapping by limited proteolysis and subsequent slab gel electrophoresis. Patient but not donor cells were able to actively synthesize a M.W. 78,000 protein that could be precipitated with goat anti-SSV. An enzyme with properties of reverse transcriptase was increased 30-fold ion patient cells when compared with donor and other control cells. Related to the presence of widespread infectious agents may be the finding that, in the course of the patient's disease, donor serum showed increasing amounts of possibly immunoregulatory (Cancer Research, submitted for publication) antibodies, reactive with autologous and, more effectively, with patient-derived cell membrane M. W. 80,000 protein (a possible idiotypic receptor structure) and M.W. 94,000 protein (a T-cell alloantigen).
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PMID:Synthesis of a viral protein with molecular weight of 30,000 (p30) by leukemic cells and antibodies cross-reacting with Simian sarcoma virus p30 in serum of a chronic myeloid leukemia patient. 617 17

Visna virus is a retrovirus which replicates in fibroblast-like cells of the sheep choroid plexus through a lytic cycle. Visna virions contain three major low-molecular-weight proteins (p30, p16, and p14) which, together with the genomic RNA and several molecules of reverse transcriptase, constitute the core structure of the virions. The core is surrounded by an envelope containing a major glycoprotein (gp135). By analogy with the oncoviruses, these three groups of structural proteins (i.e., the internal proteins, the envelope glycoprotein, and the reverse transcriptase) are probably encoded by the gag, env, and pol genes, respectively. To elucidate the genetic organization of the visna virus genome and its expression, we studied the synthesis of viral proteins in infected sheep choroid plexus cells. Intracellular viral proteins were detected by immunoprecipitation of pulse-labeled cell extracts with monospecific sera raised against p30, p16, and gp135 and resolution of the proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoprecipitation with anti-p30 and anti-p16 sera allowed the characterization of the 55,000-dalton polypeptide precursor to internal virion proteins p30, p16, and p14 (Pr55(gag)). Tryptic peptide mapping confirmed the precursor-product relationship between Pr55(gag) and the three internal proteins. In addition, a gag-related polypeptide of 150,000 daltons was also detected. This polypeptide, which was less abundant than Pr55(gag), is a likely precursor to the viral reverse transcriptase (Pr150(gag-pol)). Pr55(gag) and Pr150(gag-pol) are not glycosylated. The precursor related to major envelope protein gp135 is a glycosylated polypeptide with an average molecular weight of 150,000 (gPr150(env)). Pulse-chase experiments indicated that gPr150(env) matures into glycoprotein gp135 intracellularly; however, gp135 was never preponderant in cell extracts. The non-glycosylated from of gPr150(env), which accumulated in the presence of 2-deoxy-d-glucose, appeared as a polypeptide of about 100,000 daltons. These results indicated that visna virus codes for the largest non-glycosylated env-related precursor among all of the retroviruses and therefore probably contains the largest env gene.
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PMID:Precursor polypeptides to structural proteins of visna virus. 617 45

Tissues obtained at necropsy from a 7 year old male gibbon ape with malignant lymphoma and leukemia were analyzed by electron microscopic, immunological and enzymological techniques to determine the comparative localization of tumor cells and virus throughout the body. In general, the different assays correlated well; the reverse transcriptase (RT) assay and p30 radioimmunoassay (RIA) being the most sensitive, although the RT assay was able to detect activity in one tissue scored negative by p30 RIA. Tissues were infiltrated with tumor cells to varying degrees which correlated well with the level of virus markers in most cases with the exception of the liver and kidney. In these 2 organs there was marked infiltration of free virus and tumor cells but there was no evidence of virus infection or production by these cells.
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PMID:Comparison of the tissue distribution of reverse transcriptase, p30 and type-C virus in a gibbon ape with lymphocytic leukemia. 618 17

Postmitochondrial cytoplasmic extracts, prepared from uninfected NIH/3T3 cells as well as from chronically or exogenously infected with murine leukemia virus (MLV), were found to stimulate the endogenous reaction of purified MLV reverse transcriptase. No such stimulation was observed with the exogenous reaction of this enzyme, using poly (rA) oligo (dT) as an exogenous template-primer. While the stimulatory capacity of extracts from uninfected and chronically infected cells was comparable, that of the exogenously infected cells was much more powerful in this respect. The stimulatory activity could be destroyed by trypsin, indicating that it was excerted by a protein. In uninfected and chronically infected cells this protein was found to be of a short functional life time under conditions blocking continuous protein synthesis. However the mRNA coding for this factor was found in these cells to be stable. On the other hand, the increased stimulatory activity, observed in extract of exogenously infected cells, was independent on protein synthesis and therefore was attributed to a protein apparently introduced into the cells by the penetrating virions. Experiments with monospecific antibodies against MLV proteins suggested that p30 is an important accessory for reverse transcriptase activity and that the cytoplasmic stimulatory factor might be also related to p 30.
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PMID:Evidence for a cytoplasmic factor regulating murine leukemia virus DNA synthesis and its preliminary characterization. 618 43


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