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)

The effect of glucocorticoids on activation and replication of leukemia virus in AKR mouse embryo cells was analyzed. The number of cells detected as positive by fluorescent antibody techniques as well as the virus production in cells chronically producing virus was doubled at optimal concentrations of glucocorticoids. The effect of the hormones in activated cells was found to be not on the process of activation per se but rather on synthesis of the viral components after activation has occurred. Intracellular reverse transcriptase levels were not changed by hormone treatment. The stimulation of virus synthesis by glucocorticoids requires binding of the steroid to a cytoplasmic receptor protein.
Cancer Res 1975 Feb
PMID:Effect of glucocorticoids on activation of leukemia virus in AKR mouse embryo cells. 4 95

Particulates with the properties of cores and/or ribonucleoproteins of RNA tumor viruses have been isolated from Sterox-SL-treated fractions of murine and human mammary adenocarcinomas. These particulates have an RNA-directed DNA polymerase, a 60 to 70 S RNA, and a density of 1.26 g/ml or greater in sucrose equilibrium density gradients. Their uniquely higher densities lead to banding in regions comparatively free of cellular contaminants. These circumstances minimize some of the technical complications of performing the simultaneous detection assay in the presence of cell debris.
Cancer Res 1975 Apr
PMID:Biochemical characterization of putative subviral particulates from human malignant breast tumors. 4 81

A hamster syncytium-forming ("foamy") virus (HFV) was characterized. The HFV sedimented in isopyknic sucrose density gradients at 1.16-1.165 g/ml. It had RNA but no DNA, its replication was inhibited by actinomycin D, and it contained virion-associated, RNA-dependent DNA polymerase. Analysis of the RNA from purified virus showed several species: 62S, 40S, 28-30S, 18-20S, and 4-7S.
J Natl Cancer Inst 1975 Mar
PMID:Biochemical properties of a hamster syncytium-forming ("foamy") virus. 4 98

The results of molecular hybridization experiments with high-molecular-weight RNA isolated from RNA tumor viruses and DNA from normal cells suggest that RNA tumor virus genomes originate from cell genes. Some RNA tumor viruses (here called class 1) appear to have been generated in recent times in that their RNA is closely related in nucleotide sequence to certain cell genes (class 1 genes). A second class of RNA tumor viruses (here called class 2) is more distantly related to genomic information of normal cells. Structural properties of the RNA of RNA tumor viruses lead us to propose that the tumor virus RNA is originated when RNA transcripts of class 1 genes are processed by a mechanism we call "paraprocessing." We postulate that RNA paraprocessing is normally used only at particular times during differentiation and is characterized by the cytoplasmic appearance of high-molecular-weight RNA chains containing terminal polyadenylic acid (200 residues). Paraprocessing of class 1 gene transcripts in committed or differentiated cells is considered to be aberrant in transcription that can lead to the generation of an RNA tumor virus genome. If the paraprocessed class 1 gene transcript codes for a reverse transcriptase, replication of the RNA becomes possible. Transfer of the replicating RNA to a new cell can result in genetic change such that the virus genome mutates, differing from the original progenitor genes. We propose that this genetic change causes class 1 viruses to become class 2. These ideas are applied to evidence concerning the biology of infection of RNA tumor viruses and concerning the involvement of RNA tumor viruses in human cancer. Genetic change can also occur during the origination of an RNA tumor virus genome by repeated reverse transcription and recombination (45) or by genetic alteration of particularly changeable cell genes ("hot spots") (43).
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PMID:RNA processing and RNA tumor virus origin and evolution. 4 50

Morphologic, tissue culture, immunologic, and biochemical methods have been used in an attempt to detect and characterize oncogenic viruses or their subviral components in cells derived from human prostatic carcinoma (PrCa) or benign prostatic hyperplasia (BPH). Electron microscopy was used to characterize the ultrastructural features of normal and neoplastic prostatic tissue. Examination of specimens of prostatic tissue from 34 patients with PrCa, ten patients with BPH, and three patients with bladder tumor (BT) revealed the presence of particles resembling type-C virus in three cases of PrCa and structures resembling budding type-C virus particles in one case of BPH. Fifty human prostatic tissue specimens have been set in tissue culture, of which 30 have been successfully grown for varying periods of time. Of 20 currently active cultures, nine consist primarily of epithelial cells. Immunofluorescence and mixed hemadsorption tests of cells derived from benign and malignant prostatic tissue and sera derived from patients with PrCa, BPH, BT, and other types of tumors, and from normal donors revealed that sera from patients with PrCa, BPH, or BT contain antibodies to antigens in cells derived from PrCa, BPH, or BT. The nature of these antigen-antibody reactions is under study. Initial biochemical studies have not detected reverse transcriptase in the tissue culture fluid from a small number of sparsely growing PrCa cultures nor specific gene sequences homologous to murine leukemia virus-Rauscher genomic RNA in preparations of either normal or malignant prostatic cell DNA. The results of these preliminary studies have demonstrated the applicability of the techniques employed to the study of the relationship of viruses to human PrCa and have provided a number of promising leads for further investigation.
Cancer Chemother Rep
PMID:Virologic and immunologic studies of human prostatic carcinoma. 4 14

SV-40-transformed hamster prostatic tissue has been previously evaluated as a model for human prostatic carcinoma. Because the original cell line was lost, Syrian golden hamster prostatic tissue has been established in explant culture and infected with a 10-6-cell tissue culture infectious dose (50 percent effective) of SV40. After in vitro transformation, the cells were produced in quantity and 60 times 10-6 cells were injected into adult male Syrian golden hamsters 24 hours after 400 rads of whole-body radiation. After 60-90 days, a small palpable tumor developed. These tumors could be serially transplanted in adult male animals without immunosuppression. The tumor cells were established in tissue culture and the cells were returned to adult animals without immunosuppression where they rapidly produced fast-growing tumors. The solid tumors were composed of sheets of pleomorphic polygonal cells with large nuclei and many nucleoli; they resembled undifferentiated human prostatic carcinoma. In vitro, the cultures contained small, rapidly growing cells with a population doubling time of about 1.3 days. The cells carried the SV 40-specific antigen. The modal chromosome number was 66-68 with a distribution of 47-120. Cells exposed to 2-bromo-5'-deoxyuridine in culture did not release particles with RNA-dependent DNA polymerase activity. Endocrine sensitivity in vivo and in vitro is undertermined to date.
Cancer Chemother Rep
PMID:Properties of prostatic cultures transformed by SV40. 4 16

The "virogene-oncogene" hypothesis of Huebner and Todaro and the "provirus" hypothesis of Temin implicate RNA tumor viruses in the neoplastic transformation of mammalian cells. These hypotheses have been substantiated in several animal systems including primates and, presumably, in man. Because the detection in a tissue of one or two activities allegedly related to RNA tumor virus may not be conclusive evidence for viral presence, we have developed a scheme of coordinated morphologic, biologic, and biochemical investigations of human prostatic tissues. We report here the more recent progress we have made in one of the segments of our scheme of investigations. Two, possibly three, DNA polymerase activities from human prostatic tissue have been isolated and partially purified by DEAE-cellulose and phosphocellulose chromatography. These activities have been partially characterized. Based on template preferences and non-inhibition by selective inhibitors of reverse transcriptase, neither of the major polymerase activities appears to be the reverse transcriptase-type activity.
Cancer Chemother Rep
PMID:The search for "virogene" in human prostatic tissues: prostatic DNA polymerases. 4 15

Carbaryl(N-methyl-1-naphthylcarbamate) and its nitrosated product, N-nitrosocarbaryl, were tested for their effects of BALB/3T3 (clone A31) cells in culture. Nitrosocarbaryl, but not carbaryl, caused transformation of the BALB/3T3 fibroblasts, but neither chemical induced the complete expression of endogenous murine leukemia virus. Transformed cells differed from the parental control cells by loss of contact inhibition, change in morphology, growth in soft agar, growth to higher saturation densities, and tumorigenicity in normal newborn and irradiated weanling mice and athymic (nude) mice. Transformed clones were found to be negative for expression of RNA tumor virus antigens, viral reverse transcriptase, and infectious virus. Thus, it appears that nitrosocarbaryl can transform BALB/3T3 cells to tumorigenic cells with altered biological properties but without complete activation of RNA tumor viruses in the transformed cells. Expression of viral antigen in the transformed cells was inducible by iododeoxyuridine, indicating that the endogenous viral genome was retained in an unexpressed state.
Cancer Res 1975 Oct
PMID:Effects of nitrosocarbaryl on BALB/3T3 cells. 5 Aug 78

At concentrations of 7 times 10(-6) to 7 times 10(-5) M, derivatives consisting of the polycylic ring structures fluoranthene, fluorenone, fluorene, anthraquinone, xanthenone, and dibenzofuran with appropriate amine side chains inhibited by over 90% the purified RNA-directed DNA polymerase of avian myeloblastosis virus acting on poly(deoxyadenylate-deoxythymidylate) [poly(dA-dT)]. Of these, only the fluoranthene derivatives were strong inhibitors of the viral DNA polymerase directed by polyadenylate-oligodeoxythymidylate [poly(A)-(dT)12-18]. Low levels of fluoranthene derivatives (1 times 10(-5) M) also strongly inhibited polymerase with polyinosinate-oligodeoxycytidylate [poly(I)-(dC)12-18], activated calf thymus DNA, and viral 70S RNA as templates, but not with polycytidylate-oligodeoxyguanylate as template. A comparison of the activity of 11 fluoranthene derivatives with different side chains showed that the structure of the amine side chain influenced both the extent of antipolymerase activity with a given template and the relative inhibition with different synthetic DNA and RNA templates. The naturally occurring polyamines, spermine, spermidine, and putrescine, did not inhibit the activity of the viral DNA polymerase. Studies on the mechanism of action indicated that the synthetic derivatives inhibited polymerase activity by binding to the template and not to the enzyme: 1) inhibition by fluoranthene derivatives was overcome by the addition of excess template including poly(dA-dT), poly(A)-(dT)12-18, poly(I)-(dC)12-18, viral 70S RNA, and activated calf thymus DNA; 2) the degree of inhibition by fluoranthene derivatives was unaffected by the addition of the creased viral DNA polymerase; 3) with the same template, Escherichia coli DNA-directed RNA polymerase and the viral RNA-directed DNA polymerase were inhibited to about the same extent; and 4) the derivatives formed a complex with DNA, poly(I), and poly(A) that was stable to exclusion chromatography on Sephadex G-100. Several derivatives also had biologic activity, since they blocked the ability of the murine sarcoma virus to transform cells.
J Natl Cancer Inst 1975 Aug
PMID:Inhibition of purified DNA polymerase of RNA tumor viruses by fluoranthene derivatives and analogues of tilorone hydrochloride. 5 Oct 87

A particle fraction with a density of 1.15-1.19 g/cm3 was isolated from the cytoplasm of a human cell line established in culture from the bone marrow of an untreated patient with polycythemia vera. Electron micrographs of cross sections of cells and cell homogenates revealed virus-like particles on which DNA could be synthesized. An RNA-dependent DNA polymerase, isolated from the particles, preferred poly(rA)-oligo(dT) over poly(dA)-oligo(dT) and was able to polymerize deoxyguanosine monophosphate in a reaction stimulated by poly(rC)-oligo(dG).
J Natl Cancer Inst 1975 Sep
PMID:Particle-associated RNA dependent DNA polymerase and high-molecular-weight RNA in a human cell line derived from polycythemia vera bone marrow. 5 Oct 88


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