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 isolated from a spontaneous mammary carcinoma of a rhesus monkey and propagated in human cells possess an RNA-instructed DNA polymerase. They also exhibit DNA polymerase activities that respond to either double-stranded DNA or synthetic RNA.DNA hybrid complexes as templates. The virion has been shown to have a density of 1.16 g/ml and to contain a nucleic acid species of high molecular weight (sedimentation coefficient, 60-70 S), which bands as RNA at 1.670 in a Cs(2)SO(4) equilibrium density gradient. In addition, the virions contain species of low molecular weight (4-6 S) that consist of RNA as well as components banding at densities characteristic of DNA.RNA complexes. The nucleoid of this virion has been isolated and shown to have a density of 1.23 g/ml; it also contains a 60-70S nucleic acid species.
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PMID:DNA polymerase activities and nucleic acid components of virions isolated from a spontaneous mammary carcinoma from a rhesus monkey. 528 52

The expression of MuMTV and MuLV major polypeptides and extracellular revertase activity (RA) in relation to the treatment with insulin (INS), dexamethasone (D) or both hormones was studied in four clones derived from two mammary carcinoma (MC) stable cell lines, RIII/mt and GR/mt. In the cells growing in media without hormonal supplementation or with either insulin or dexamethasone alone the expression of p27 MuMTV was poor, in cultures treated with dexamethasone alone a slight increase in Mg++-dependent RA could be detected suggesting formation of A particles. A 10-fold increase of RA and gp52 MuMTV expression resulted only from the treatment with insulin which induced visible morphological changes in the cells from fibroblast-like towards epithelium-like patterns and formation of "domes". The hormones studied exerted no detectable effect on the MuLV genome expression.
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PMID:[Hormone-dependent expression of oncovirus genomes in stable mouse mammary cancer cell line GR and RIII]. 616 17

Sheep pulmonary carcinoma (SPC) has been shown to be associated in nature with a retrovirus, by electron microscopic, biochemical, and epidemiological criteria and by experimental transmission. In this study, a retrovirus has been isolated from SPC tumors which were experimentally induced by inoculation with a cell-free, reverse transcriptase containing fraction from a spontaneous field case of SPC, and propagated in culture. This novel virus was shown to be unrelated to murine, avian, and bovine leukemia viruses, to be exogenous to the ovine species, and to have only limited genetic relatedness to the lentiviridae (maedi-visna and caprine arthritis encephalitis virus).
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PMID:Isolation and characterization of a novel retrovirus from sheep affected by pulmonary carcinoma. 632 72

Clonal derivatives 8 and 11 of the T47D human breast carcinoma cell line release particles that have the biochemical characteristics of a retrovirus. Particles recovered from cultures of [3H]uridine-labeled clone 11 had a density of 1.18 g/ml and contained 60-70S and 35S RNAs associated with reverse transcriptase activity. The production of these particles was steroid-dependent. Clone 8 particles had a higher density, 1.195 g/ml, and their production was independent of steroid hormone. By RIA, antigens crossreactive with the 52,000-dalton envelope glycoprotein gp52, the major external protein of mouse mammary tumor virus, were found associated with these particles and in the media. Most of the gp52-related antigen was in soluble form, but it was enriched in the particle preparation. A lesser amount of antigen was distributed within the cultured cells. Absorption of rabbit antibody to gp52 with clone 11 particle preparations eliminated the ability of this antibody to detect immunocytochemically a crossreactive antigen previously localized in tissue sections of human breast carcinoma. These results indicate that the particle isolates from T47D contain the same gp52-related antigen found in human breast carcinomas and constitute an excellent source for the purification and characterization of this antigen.
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PMID:Properties of retrovirus-like particles produced by a human breast carcinoma cell line: immunological relationship with mouse mammary tumor virus proteins. 633 Jul 48

The processing of gag-gene-coded polyproteins of type D retrovirus (HEp-2 V) in chronically infected continuous human larynx carcinoma cell line HEp-2 (HeLa-like) was investigated by means of the pulse-chase modification of the radioimmunoprecipitation test. Three independent polyproteins coded by the gag gene of HEp-2 V were revealed in the immunoprecipitates: Pr 78gag, a direct precursor of the virus internal structural polypeptides, described in a previous report (1); Pr 180gag + pol, a probable reverse transcriptase precursor; and gPr 78gag, a glycosylated polyprotein of unknown function. Two unstable intermediate polyproteins derived from Pr 78gag cleavage were detected in the presence of serine protease inhibitors. These polypeptides, having molecular weights of 37 K and 33 K, are Pr 37gag and Pr 33gag respectively. A probable scheme of gag-gene-coded polyproteins processing is suggested, and speculations on the gag-gene-coded glycosylated polyproteins of retroviruses as growth factor receptors are also presented.
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PMID:Three independent polyproteins coded by the gag gene of type-D retrovirus in a continuous human cell line. 633 3

Embryonal carcinoma (EC) cell lines established from human testicular germ-cell tumours produce, at low frequency, virions morphologically identical to type C retroviruses that have been observed by other workers in human placental tissues. The virus particles are formed while budding from the cell surface, and their numbers are increased by inducing the EC cells with 5-iodo-2'-deoxyuridine and dexamethasone. Assays for RNA-dependent DNA polymerase (reverse transcriptase) associated with purified virions suggested a low level of activity. In addition, another type of virus is occasionally produced by induced cells of three EC lines. These particles also form during the process of budding from the cell surface, but they have surface projections (spikes). Extracellular spiked virions frequently are pleomorphic, with a condensed, eccentric nucleoid, and thus morphologically resemble type B retroviruses. No virions of either type were detected with or without induction in cultures of differentiated EC cells or in cultures of yolk sac carcinoma or teratoma cells, both of which are considered malignant but differentiated derivatives of EC cells. The lack of virion production by these differentiated cells suggests developmental regulation of virus replication.
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PMID:Production of virions with retrovirus morphology by human embryonal carcinoma cells in vitro. 672 85

The met proto-oncogene receptor tyrosine kinase has been identified as a receptor for hepatocyte growth factor (HGF)/scatter factor (SF). HGF/SF is a multifunctional cytokine that stimulates mitogenesis, dissociation, and motility of a broad spectrum of epithelial and endothelial cells in culture, promotes the progression of carcinoma cells to a more invasive phenotype, and acts as a morphogenic factor for tubular epithelia. HGF/SF is predominantly expressed by mesenchymal cells, whereas the met/HGF/SFR is predominantly expressed by epithelial and carcinoma cells in culture. We have shown by Northern analyses that the met/HGF/SFR is expressed in many adult mouse tissues. To elucidate the normal physiologic role for the met/HGF/SFR and the possible pathologic consequences of deregulation of this pathway, we have examined the expression of the met/HGF/SFR in adult mouse tissue by in situ hybridization. We show that the met/HGF/SFR is generally expressed in epithelia, including hepatocytes, epithelial cells that line the proximal and distal convoluted tubules of the kidney, epithelia of stomach, esophagus, uterus, lung and skin, as well as in granulosa cells of developing and mature oocytes. By reverse transcriptase PCR amplification, we show that the HGF/SF gene is expressed at low levels in many of these tissues. Our data support a possible role for the met/HGF/SFR in epithelial cell growth and tissue organization.
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PMID:Expression of the hepatocyte growth factor/scatter factor receptor tyrosine kinase is localized to epithelia in the adult mouse. 747 19

Three species of E6/E7 cDNAs of human papillomavirus type 16 (HPV16) for the full-length E6/E7 and spliced E6*I/E7 and E6*II/E7 mRNAs were synthesized by reverse transcriptase-(RT-)PCR from RNA of the cervical carcinoma cell line SiHa. Two cDNA mutants carrying point mutations in either a splice donor site or acceptor site within the E6 open reading frame were also constructed. These HPV16 E6/E7 cDNAs were cloned under the SV40 enhancer/promoter and the MMTV LTR to examine the activities of ras-collaborative transformation and induction of cellular DNA synthesis, both of which depend on the E7 gene product. The E6*II/E7 cDNA and two mutated cDNAs deficient in the spliced mRNA transcription showed lower levels of both activities than the full-length E6/E7 and the E6*I/E7 cDNA. The rat cell lines carrying each of the E6/E7 cDNAs contained the E6/E7 mRNA species expected. A small amount of E6*I/E7-sized mRNA was transcribed from a splice-donor site mutant of the E6/E7 cDNA, which turned out to be a transcript derived from a cryptic splice donor site six bases upstream from the conventional site. Among NIH3T3 cells carrying one of the above-mentioned E6/E7 cDNAs, the cells expressing E6*I/E7 mRNA [cells carrying cF(wt) and c*I] produced an amount of E7 protein comparable with those carrying the E7 or E6E7 region. These results suggest that the E6*I/E7 is the mRNA that is important for the efficient expression of E7 product from the HPV16 E6/E7 region.
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PMID:Biologic activity of human papillomavirus type 16 E6/E7 cDNA clones isolated from SiHa cervical carcinoma cell line. 748 85

In human long-term marrow cultures granulomonopoiesis is maintained for several weeks. Studies on granulomonocytic progenitors (CFU-GM) and their progeny have shown that survival, proliferation, differentiation and maturation of these cells are controlled by a set of glycoproteins, the colony-stimulating factors (CSFs) and the Steel factor. We have studied the expression of these factors using reverse transcriptase polymerase chain reaction (RT-PCR) in 17 adherent layers of normal bone marrow at 3, 5 or 7 weeks of culture. We have taken the 5637 bladder carcinoma cell line as a control for expression of GM-CSF, M-CSF, G-CSF and Steel factor, and PHA-activated T lymphocytes as a control for expression of multi-CSF (interleukin 3, IL-3). We have found that GM-CSF was expressed in the 17 adherent layers without induction by interleukin 1 beta (IL-1 beta). M-CSF was also detected in all cases, but in two early-stage (week 3 and week 5) cultures only after stimulation by IL-1 beta. G-CSF was detected in only 11 cases (three without IL-1 beta, and eight after addition of IL-1 beta). Steel factor was detected in 14 cases (ten without IL-1 beta, and four after addition of IL-1 beta). IL-3 was not detected even by means of nested RT-PCR. These data indicate in six late-stage (week 5 or week 7) cultures G-CSF messenger concentrations 10(3)-fold less than in 5637 control cells (for an identical amount of total cellular RNA). A similar conclusion may be drawn for Steel factor in three late-stage cultures. For IL-3 our negative results indicate a messenger concentration 10(5)-fold less than in activated T lymphocytes. These results suggest a crucial role for GM-CSF and M-CSF in the maintenance of granulomonopoiesis in human long-term cultures. The role of G-CSF and Steel factor may be more marginal. Eventually IL-2 may not be involved in the regulatory process.
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PMID:The detection of colony-stimulating factors and steel factor in adherent layers of human long-term marrow cultures using reverse-transcriptase polymerase chain reaction. 751 Mar 57

Changes in the CD44 variant (CD44v) isoforms on the cell surface have been correlated with tumor metastasis. In this study we have examined the expression of CD44 variant isoforms in human breast carcinoma samples by a variety of techniques including immunohistochemistry, reverse transcriptase-polymerase chain reaction (RT-PCR), and nucleotide sequencing. Using RT-PCR, we have determined that normal human breast tissue contains primarily the CD44 epithelial (CD44E) form and very little CD44 standard (CD44s) form. However, metastatic breast carcinomas appear to overexpress both the CD44E and CD44s forms and also display multiple new species of CD44 variant isoforms. Histocytochemical staining using anti-CD44 antibody (recognizing a common determinant of the CD44 class of glycoproteins) confirms that the CD44 molecules are overexpressed and preferentially located in metastatic breast cancer tissues. Nucleotide sequencing analyses indicate that at least four new CD44 variant isoforms (i.e., displaying unique splicing via the insertion or the deletion of exons 7, 10, 11, and 14) may be closely associated with human metastatic breast cancers. These newly described CD44 variant isoforms may be useful for monitoring the progression of human breast cancer metastasis.
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PMID:New CD44 splice variants associated with human breast cancers. 752 35


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