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 expression of Thy 1.2 (theta C3H) antigen was measured on the membranes of normal and neoplastic RIII and C3H mammary cells. Competitive inhibition assays revealed that the average membrane content of Thy 1.2 in mammary tissues was about equal to that of lymph node cells. Higher percentages of Thy 1.2-positive cells than mammary tumor virus (MuMTV)-positive cells were observed by immunofluorescence, which suggested that not all the Thy 1.2-positive cells recovered from tumors were also MuMTV-positive. Established tissue culture cell lines C3H and RIII MT expressed lower levels of Thy 1.2 than did cells from mammary tumors. Treatment with the synthetic gluco-corticoid dexamethasone increased the average Thy 1.2 expression in cultured mammary tumor cells as well as the levels of RNA-directed DNA polymerase. Since the percentages of Thy 1.2-positive cells also were greater in steroid-treated cultures, while fewer cells were needed to absorb a standard amount of anti-Thy 1.2 activity, it was concluded that dexamethasone enhanced membrane Thy 1.2 expression as well as MuMTV production by the cultured cells.
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PMID:Expression of Thy 1 antigen in normal and neoplastic mammary cells of mice. 19 40

The presence of virus-specific RNA in mammalian tumour cell lines of RSV aetiology was studied using molecular hybridization between the PR-RSV 3H-DNA probe synthetized by the endogenous RNA-directed DNA polymerase reaction and cellular RNA. It was found that both virogenic XC cells harbouring the full PR-RSV genome and cryptovirogenic RVP3 cells harbouring an incomplete PR-RSV genome contain virus-specific RNA. The degree of homology between such RNA and PR-RSV 3H-DNA probe reached 10--12% in XC cells and 28--30% in RVP3 cells. It was found that RVP3 cells contain larger amounts of virus-specific RNA than XC cells and that it is localized in the gradient zone corresponding to 20--25S.
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PMID:Virus-specific RNA in selected cell lines derived from RSV-induced tumour. 19 54

An RNA-directed DNA polymerase was purified from baboon endogenous type-C virus by successive column chromatography on DEAE cellulose, phosphocellulose and hydroxyapatite. The purified DNA polymerase has a molecular weight of 68 000, a pH optimum of 8.0, a Mn2+ optimum of 1 mM, and a KCl optimum of 40 mM. The purified enzyme transcribes heteropolymeric regions of viral 60--70 S RNA isolated from different type-C viruses. The purified enzyme is immunologically related to a similarly purified polymerase from the cat endogenous type-C virus RD114.
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PMID:Purification and characterization of baboon endogenous virus DNA polymerase. 20 Feb 68

DNA was extracted from two human sarcoma cell lines, TE-32 and TE-418, and the leukemic cells from five children with acute myelocytic leukemia, three children with acute lymphocytic leukemia and four adults with acute myelocytic leukemia. The DNAs, assayed for infectivity by transfection techniques, induced no measurable virus by methods which would detect known mammalian C-type antigens or RNA-directed DNA polymerase in TE-32, D-17 dog cells and other indicator cells, nor did they recombine with or rescue endogenous human or exogenous murine or baboon type-C virus. Model systems used as controls were human sarcoma cells, TE-32 and HT-1080, and human lymphoma cells TE-543, experimentally infected with KiMuLV, GaLV or baboon type-C virus, all of which released infectious virus and whose DNAs were infectious for TE-32 and D-17 dog cells. Other model systems included two baboon placentas and one embryonic cell strain spontaneously releasing infectious endogenous baboon virus and yielding DNAs infectious for D-17 dog cells but not for TE-32 cells. Four other baboon embryonic tissues and two embryonic cell strains, releasing either low levels of virus or no virus, did not yield infectious DNA.
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PMID:Search for infective mammalian type-C virus-related genes in the DNA of human sarcomas and leukemias. 20 87

Electron microscopic examination of mink lung cells previously cultured with a squirrel monkey (Saimiri sciureus) throat swab suspension revealed the presence of squirrel monkey retrovirus (SMRV) and Herpesvirus saimiri (HVS) coexisting within the same cells in culture. HVS was identified by serum neutralization, and the retrovirus isolate was identified as SMRV by a morphologic examination, microimmunodiffusion analysis, and demonstration of an Mg2+ preference for the RNA-directed DNA polymerase.
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PMID:Squirrel monkey retrovirus and Herpesvirus saimiri: observation in the same cell following isolation. 22 4

Sucrose density gradient analysis of purified pancreatic homogenates from glycaemic C57BL/Ks diabetes (db/db) mice and their normoglycaemic controls have revealed the presence in the diabetics of increased Mg++-dependent RNA-directed DNA polymerase activity sedimenting with a density of approximately 1.21 g/cm3. Electron microscopy revealed that this fraction contained typical intracisternal A-particles. Purified cultures of pancreatic islet cells 4--7 day old postnatal "misty diabetic" mice and normal siblings were established and then maintained in Eagle's minimal essential medium without serum. Under these conditions, the presence of intracisternal A-particles in beta cells of both mutant and control genotypes was very rare. No change in numbers of intracisternal A-particles was seen after 2--4 days of incubation in Dulbecco's-modified minimal essential medium containing 5.5 mmol/l glucose. However, when the glucose concentration of Dulbecco's medium was elevated to 16.5 mmol/l, ultrastructural changes specific to the beta cell population occurred that were reminiscent of those alterations observed in situ. Intracisternal A-particles were commonly seen in cultured beta cells showing hypersecretion-stress morphology. Since equal numbers of intracisternal A-particles were present in cultured beta cells from normal and mutant mice, it was concluded that the db gene itself was not required for intracisternal A-particle expression. The cell culture results suggest that elevated intracisternal A-particle activity observed in vivo may be produced directly or indirectly by the ambient high blood glucose levels characteristic of this mutant.
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PMID:Intracisternal A-particles in genetically diabetic mice: identification in pancreas and induction in cultured beta cells. 22 51

An RNA-directed DNA polymerase was purified from bovine leukemia virus (BLV) by successive glycerol gradient centrifugation, column chromatography on phosphocellulose and gel filtration on Sephadex G-200. The purified DNA polymerase transcribes heteropolymeric regions of 30--40 S RNA isolated from avian myeloblastosis virus. The enzyme differs from other known DNA polymerases of mammalian type-C RNA tumor viruses by the following properties: 1. Its apparent molecular weight as estimated by velocity sedimentation data is 58,000 at 0.12 M KCl and 43,000 in the presence of 0.50 M KCl. 2. It has a Mg2+ optimum of 10 mM, and a Mn2+ optimum of 0.25 mM with (rA)n-(dT)10 as template. 3. At 50 mM KCl it is inhibited more than 70%, but it is not inhibited by phosphate ions at 2 mM. These properties confirm the peculiar position of BLV within the family Retraviridae.
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PMID:Purification and characterization of bovine leukemia virus DNA polymerase. 23 43

In view of recent developments, the structural determinants of the interferon inducing activity of polynucleotides have been (re)evaluated. To induce interferon, the polynucleotide should be sufficiently large and double-stranded, although not necessarily double-stranded over its whole length. It should be sufficiently stable to both thermal denaturation and hydrolysis by nucleases. It should also contain a particular steric conformation. This conformation is most regularly ensured by the presence of 2'-hydroxyl in the ribose moieties and intact purine-pyrimidine base pairs in the interior of the double helix. Other biologic activities of polynucleotides, such as anti-complement activity and inhibition of reverse transcriptase (RNA-directed DNA polymerase) activity, depend on structural requirements which are rather antagonistic to those governing the interferon response.
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PMID:Interferon induction by polynucleotides: structure-function relationship. 35 56

Experimental tumors developed in white Pekin ducks after intramuscular implantation of 20-methylcholanthrene. Cells derived from the primary tumor were adapted successfully to grow in vitro and have growth characteristics similar to that of established cell lines of mammalian origin. The cell density rises rapidly and the doubling time is approximately 17 hr. The duck cells have been cultured successfully for at least 80 passages in votro. The continuously cultured cells have the characteristic chromosome pattern of duck, and the DNA of the duck cell line hybridized with duck liver DNA. We believe we have established a continuous cell line of avian origin. Electron-microscopic examinations of the tumor cells and RNA-directed DNA polymerase of the cell-free supernate show no evidence of endogenous virus production.
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PMID:Establishment of duck cell line derived from experimental tumor induced by 20-methylcholanthrene. 56 48

Conditions are described under which poly(A) polymerase from Escherichia coli ribosomes will catalyse the addition of AMP residues onto the 3'-ends of human 18 S and 28 S ribosomal RNAs at an average rate of 40 AMP residues per 1000 nucleotides in 20 min. Single-stranded complementary DNAs (cDNAs) can then be transcribed from the polyadenylated RNAs with RNA-directed DNA polymerase from avian myeloblastosis virus. All of the sequences in the RNAs are represented in the cDNAs; measurements of the rates at which the cDNAs hybridize with their template RNAs showed that, when appropriate adjustments for differences in lengths and G + C contents of the reacting sequences are taken into account, the Rot 1/2 values of homologous RNA-cDNA hybridization reactions are directly proportional to the base-sequence complexity of the RNAs.
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PMID:Synthesis of DNAs complementary to human ribosomal RNAs polyadenylated in vitro. 78 37


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