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)

DNA-RNA hybridization was used to explore whether human neoplasias contain RNA molecules having sequence homologies to those of the RNA tumor viruses known to cause similar diseases in animals. The pattern of specific RNAs found in the human tumors showed a remarkable concordance with the predictions deducible from the animal systems. Thus human breast cancer contains RNA homologous only to that of the murine mammary tumor virus (MMTV). Human leukemias, sarcomas, and lymphomas (including Hodgkin's and Burkitt's) all contain RNA with sequence homology to the murine leukemia virus (RLV) and not to MMTV RNA. Finally, as in the case of the mouse, none of the human tumors examined contain RNA related in sequence to that of the avian myeloblastosis virus (AMV). The RNA detected in all of the human neoplasias was demonstrated to be of high molecular weight (1 times 10(7) daltons) and encapsulated with a reverse transcriptase in particles having densities between 1.16-1.19 g/ml. Further, the RNA of these human tumor particles was related in sequence to the murine viruses that cause the corresponding neoplasias in mice. Thus, 4 features diagnostic for the murine oncogenic viruses are satisfied by the particles found in the human cancers. Finally, it was shown by "recycling" experiments that the DNA from human leukemic cells and from lymphomatous tissue contained particle-related sequences that could not be detected in normal DNA. This finding was further substantiated by studies with identical twins in which it was shown that the leukemic twin contained particle-related sequences that could not be detected in the leukocytes of his identical healthy sibling. These findings are inconsistent with hypotheses that require chromosomal transmission in the germ line of complete copies of the information required to produce malignancy and the associated virus particles.
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PMID:Sequences related to the RNA tumor viruses in the RNA and DNA of human leukemias and lymphomas. 5 26

We isolated a type-C RNA virus from the Japanese field mouse, Mus musculus molossinus. M. musculus musculus and M. musculus molossinus are two different subspecies of Mus and thus only distantly related. The virus grew only on cells foreign to the host, was xenotropic, and readily rescued the murine sarcoma (MuSV) genome from a normal rat kidney cell line transformed nonproductively by the Harvey strain of MuSV. The virus banded at a density of 1.16 g/ml and contained an RNA-dependent DNA polymerase.
J Natl Cancer Inst 1975 Oct
PMID:Isolation of an endogenous C-type RNA virus from Mus musculus molossinus. 5 16

A virus designated bovine leukaemia virus (BLV), associated with leukaemia in cattle and previously demonstrated to induce the disease in sheep, was purified from chronically infected sheep cell cultures. Electrophoretic analysis showed a major protein of mol. wt. about 24,000 (p24) which reacted in gel diffusion and complement-fixation tests with sera from naturally infected cattle, experimentally infected sheep, and guinea pigs immunized with p24. BLV p24 has an isoelectric point of 8-6. Interspecies antigenic reactivities characteristic of mammalian Type C virus p30s were not detected in disrupted BLV or on p24. Sheep and guinea pig antisera to BLV, reactive with p24, also did not precipitate several Type C virus p30s in radioimmunoassays. BLV is also distinguished from Type C viruses and resembles mouse mammary tumour virus and Mason-Pfezer virus in having an RNA-dependent DNA polymerase which is preferentially active in the presence of Mg++ when synthetic templates are used. Along with previously published morphological data, the above indicates that BLV is not a Type C virus as classically defined. Four hundred and forty one human sera from cancer patients and matched controls were non-reactive with disruped BLV, BLV infected cells, and BLV p24 in complement-fixation tests.
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PMID:Characteristics of the major internal protein and RNA-dependent DNA polymerase of bovine leukaemia virus. 5 5

A preliminary analysis of an RNA-directed DNA polymerase was made and a C-type virus-like particle was identified in platelets from 2 patients with the myeloproliferative disorder thrombocythemia (primary, essential, hemorrhagic, or idiopathic thrombocythemia). Platelet homogenates were centrifuged through a sucrose equilibrium density gradient. Both endogenous and exogenous DNA polymerase activity was found at a density of 1.19 g/ml. No activity was seen at comparable densities in control gradients. Electron micrographs of thin sections of these platelets revealed a particle with the morphologic characteristics of a C-type virus; however, the diameter of this particle was about 80 nm, slightly lower than that commonly found for C-type particles. Critical-point dried specimens, from the fractions of the sucrose gradient at which DNA polymerase activity was found, contained particles of the same size and morphology as those in the thin sections.
J Natl Cancer Inst 1975 Nov
PMID:Analysis of platelets from patients with thrombocythemia for reverse transcriptase and virus-like particles. 5 32

T24C, a continuous cell line derived from the pooled thymic tissue of normal inbred OM rats, spontaneously produced type-C virus. The virus genome was expressed cyclically. The amount of RNA-dependent DNA polymerase (RDP) and the number of 1.14 g dense particles/ml fluctuated simultaneously with cultivation. The released virus, RPT24C, did not infect cell lines from the rat, mouse, dog, or human. T31, also a rat thymus line, during its 2.5 years of cultivation did not produce type-C virus. Cocultivation with potentially permissive lines did not rescue any virus. 5-lodo-2'-deoxyuridine treatments at earlier passages yielded negative results. Chemical treatment at passages 111, 116, 123, and 128 yielded varying amounts of 3H-uridine incorporation at a sucrose density of 1.14 g/ml. Enzyme assays on chemically treated T31 cultures tested at passage 111 showed a small but transient burst of RDP activity. T31-B, a subline of T31, which was frozen and thawed once, released rat type-C virus spontaneously at passage 56. Two additional sublines of T31 (NI-T31 and NII-T31) were maintained for 2.5 years in culture without any cell-dispersing treatment. NI-T31, but not NII-T31, spontaneously released type-C virus. Once induced, the type-C viruses from T31-B and NI-T31 were continuously produced.
J Natl Cancer Inst 1975 Dec
PMID:In vitro activation, infectivity, and production of endogenous type-C virus from OM rats. 5 37

A cat kidney cell line, CRFK-F2, was successfully inoculated in suspension and in monolayer culture with a purified mouse mammary tumor virus derived from RIII milk. The virus produced by the infected cells was identified by immunogluorescence, electron microscopy, and RNA-directed DNA polymerase assays; it was a B-type virion that did not cross-react with mouse or feline leukemia-sarcoma viruses, had spikes on its envelope, and had a RNA-directed DNA polymerase reaction that was typical of mouse mammary tumor virus. The producing cells were identified as cat cells by chromosome number, cytotoxic assays, and isoenzyme migratory patterns. A standardized method for the in vitro inoculation of cat cells is described that presently permits highly reproducible results. For the first time, the mouse mammary tumor virus is seen replicating in cells from another species, thus offering an opportunity to study the kinetics of infection of that virus.
Cancer Res 1976 Jan
PMID:Experimental infection of a cat kidney cell line with the mouse mammary tumor virus. 5 5

An inactivated and lyophilized preparation of a low virulence strain (Su) of Streptococcus pyogenes (group A) was designated OK-432. When 2- and 5-month-old AKR mice were inoculated im with OK-432 twice weekly throughout their life-spans, spontaneous leukemias occurred later and at a lower incidence than in control groups. By virus neutralization and cytotoxicity tests and by immunoelectron microscopy, antibodies against virus and cell-surface antigens of transplanted AKR leukemia were not detectable in sera of nonleukemic mice of any group. Whereas sera from mice treated with OK-432 were the only positive for interferon, viremia was clearly demonstrated in control groups by reverse transcriptase assays of the plasma.
J Natl Cancer Inst 1976 Mar
PMID:Streptococcus pyogenes preparation OK-432: immunoprophylactic and immunotherapeutic effects on the incidence of spontaneous leukemia in AKR mice. 5 50

Milk from a number of species (e.g., man, mouse, rat, dog, and cow) contains inhibitors of the RNA-directed DNA polymerase. When attempts are made to isolate virions from the milk, part of the inhibitors follow the virions in the purification. The amount of inhibitors varies in different milk samples. These inhibitors can probably account for the large discrepancies reported in studies of the presence of oncornaviruses in human milk. Phosphatases bound to subcellular particles or fragments seem to be the most important inhibitors in the milk interfering with the RNA-directed DNA polymerase assay. It is shown that the inhibitory enzymes can be completely removed by sedimentation of the milk through a Metrizamide gradient.
Cancer Res 1976 Feb
PMID:Removal of inhibitors against RNA-directed DNA polymerase activity in human milk. 5 90

The effects of poly(1-vinyluracil) [poly(vU)] and poly(9-vinyladenine) [poly(vA)] on the RNA-dependent DNA polymerase activity of murine leukemia virus (Moloney strain) were studied. Vinyl polymers themselves cannot act as templates for the polymerase. However, if a vinyl polymer is added to a polymerase reaction mixture in which a complementary polynucleotide serves as the template, the reaction is inhibited: thus with polyribocytidylic acid as template and oligodeoxyguanylic acid as primer, neither poly(vU) nor poly(vA) had a significant effect; when polyribouridylic acid was used as template and oligodeoxyadenylic acid as primer, poly(vA) inhibited polymerase activity while poly(vU) had little effect; when polyriboadenylic acid was a template and oligodeoxy thymidylic acid was a primer, poly(vU) was an inhibitor. Complex effects were noted with the latter system and poly(vA); either stimulation or inhibition of the reaction was observed, depending on the concentration of poly(vA). The stimulation brings about a decrease in the amount of lower-molecular-weight materials in the product and is caused by the interaction of poly(vA) with the template-primer. Thus vinyl polymers differ from polynucleotides in their mechanism of inhibition of viral polymerase, since the latter inhibit the enzyme by binding to it.
Cancer Res 1976 Apr
PMID:Effects of Poly(1-vinyluracil) and Poly(9-vinyladenine) on viral RNA-directed DNA polymerase. 5 95

Measurement of DNA polymerase in leukaemic guinea-pig plasms reveals the presence of low levels of sedimentable and non-sedimentable enzymic activities. Since the sedimentable DNA polymerase is ribonuclease sensitive, uses poly(C).oligo(dG) as template, and bands in a sucrose density gradient at 1-17 g/ml it is thought to be the GPLV-associated reverse transcriptase. The soluble DNA polymerase is stimulated by ribonuclease and is probably of cellular origin.
Br J Cancer 1976 Apr
PMID:DNA polymerase activity in plasma from leukaemic guinea-pigs. 5 90


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