Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

LLC-MK2 cells chronically infected with two strains of rubella virus, HPV-77 and Thomas, have been examined over several months to find out the mechanism of persistence. Evidence is given for the presence of defective particles in these cultures by finding virion RNA which sedimented at 12S instead of the 40S typical of the fully infectious virus. A 'provirus' DNA copy of the rubella virus genome was not detected by methods which included filter hybridization and in situ hybridization, or by treatment of the chronically infected cells with mitomycin C, antinomycin D or 5-bromodeoxyuridine. In addition, the chronically infected cells contained RNA-dependent RNA polymerase activity, but no RNA-dependent DNA polymerase activity.
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PMID:Mechanism of persistence of rubella virus in LLC-MK2 cells. 11 97

Human cells derived from both normal and neoplastic tissues can be infected by Mason-Pfizer monkey virus (MPMV) without accompanying cytopathology. Infection of cell cultures such as human rhabdomyosarcoma (A204) results in a persistenly infected cell line which can be subcultured over 30 sequential culture passages without significant change in phenotype properties according to reverse, transcriptase (RT), MPMV p27 antigen content, virus particle count and infectivity titre. Productive virus infections were established at relatively low virus particle (VP) input multiplicities (p.i.m.; about 0.06 VP/cell) In A204 cell cultures. At higher p.i.m. (about 600 to 6000 VP/cell) newly synthesized virus was detected within 4 days post infection. Although virus production was cumulative following primary infection, after subculture of infected cultures MPVM production was greater during active cell division. Using synchronization techniques, MPMV replication in persistently infected cultures was found to be cell cycle-dependent. The major internal antigen, p27, was synthesized in G2 and newly synthesized virus particles were released predominantly during mitosis and early G1. Colcemid arrest of cells during mitosis inhibited subsequent MPMV release. Consequently, production of extracellular virus depends upon the progression of cells through the mitotic stage. These data, which provided a basic understanding of the virus-host relationship that occurs in primate cells productively infected with MPMV, were used as a guideline for isolating MPMV-like viruses from experimentally and naturally infected Rhesus monkey.
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PMID:Characterization of infection and replication of Mason-Pfizer monkey virus in human cell cultures. 11 35

The virion-associated RNA-dependent RNA polymerase of vesicular stomatitis virus (VSV) synthesizes in vitro two size classes of RNA products similar to those observed in VSV-infected cells. One RNA product sediments at 31S with an approximate molecular weight of 2.1 X 106. The smaller products consist of at least three classes of RNA sedimenting at 17S, 14.5S, and 12S with molecular weights of 0.7 X 106, 0.52 X 106, and 0.37 X 106, respectively. Hybridization experiments show that both the 31S and 12-18S RNA products are complementary to the genome RNA, and that each class is transcribed from different nucleotide sequences. From the molecular weights of the RNA species and the hybridization experiments, it seems that almost the entire VSV genome RNA is transcribed in vitro.
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PMID:Messenger RNA species synthesized in vitro by the virion-associated RNA polymerase of vesicular stomatitis virus. 16 2

The activity of RNA-dependent RNA polymerase of several influenza viruses is stimulated by guanosine. Depending upon the virus strain used, the stimulation of initial reaction rate is up to 10-fold. 5'-GMP, 3',5'-cyclic GMP, and 5'-GDP show lesser stimulation effects. No other nucleosides of 5'-NMPs stimulate, but the dinucleoside monophosphates GpG and GpC show large stimulations. We present evidence that the stimulation represents preferential initiation of genome complementary RNA chains with guanosine: (i) [3-H] guanosine is incorporated specifically at the 5'terminus of RNA in polymerase reaction mixes in vitro. (ii) This incorporation reaction has several properties similar to those of the virion polymerase elongation reaction. (iii) RNA made in the stimulated reaction behaves as complementary RNA in annealing kinetic studies, as does RNA labeled with [3-H]guanosine.
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PMID:Influenza virion RNA-dependent RNA polymerase: stimulation by guanosine and related compounds. 16 15

Rhinovirus type 14 RNA-dependent RNA polymerase complexes were isolated from microsomal and soluble fraction of infected KB cells. Maximum activities were measured at at 6 and 7 hours post inoculation (p.i.) for microsomal and soluble polymerases, respectively. Both polymerase activities are considerably reduced by 8 to 9 hours, p.i., and interval in which the in vivo rate of synthesis of viral RNA is maximal. In vitro RNA products of RNA polymerases in both fractions consist of ribonuclease-sensitive and ribonuclease-resistant RNA of heterogeneous sizes. Detergent treatment of the microsomal RNA polymerase(s) did not affect the total amount of RNA synthesized, the proportion of ribonuclease-sensitive RNA synthesized or the size of the RNA products. The data suggest that RV14RNA polymerase complexes are intially associated with membranes but are then irreversibly released into the soluble phase of the cytoplasm; possible explanations for this phenomena are discussed.
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PMID:Rhinovirus type 14 RNA polymerase complexes. 16 77

An abortive infection of a rabbit cornea cell line (RC-60) by vesicular stomatitis virus (VSV), yielding less than 1 PFU/cell, was converted to a productive infection, yielding 1,900 PFU/cell, when cells were superinfected with vaccinia. Studies on the synthesis of VSV-directed RNA in RC-60 cells suggest that the abortive infection by VSV alone may be due in part to (i) a limited production of 40S virion RNA and (ii) a markedly reduced activity of virion-bound transcriptase activity in RC-60 cells compared to the activity in mouse L cells, a permissive host for VSV. No recognizable VSV structures, except a small amount of viral core structures, were produced by the abortive infection. In contrast, double infection of RC-60 cells with VSV and vaccinia in the presence of hydroxyurea resulted in the production of infective B particles of VSV. Although the function supplied by vaccinia responsible for the productive replication of VSV in double infected RC-60 cells has not been identified, metabolic inhibitor studies indicate that continuous vaccinia-dependent RNA synthesis is required for maximal production of infective VSV. The possibility is considered that vaccinia may supply a product or function required for VSV replication which is ordinarily supplied by the host but which is lacking in RC-60 cells.
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PMID:Abortive infection of a rabbit cornea cell line by vesicular stomatitis virus: conversion to productive infection by superinfection with vaccinia virus. 16 5

Upon infection of Chinese hamster ovary cells (CHO), vesicular stomatitis (VSV) virus synthesizes two membrane proteins (the VSV glycoprotein and the VSV matrix or membrane (M) protein) and three nonmembrane proteins (the VSV nucleocapsid, the viral transcriptase, and an NS protein). We have used the VSV-infected cell as a model system for the study of the site of synthesis of these membrane and nonmembrane proteins. We have isolated VSV mRNA from free polyribosomes, membrane-bound polyribosomes, and the postribosomal supernatant, and identified the individual species of VSV mRNA present in each fraction. The mRNA which encodes the VSV glycoprotein is found exclusively on membrane-bound polyribosomes, while the mRNAs which encode the VSV, M, N, and NS proteins are found in free polyribosomes, in the membrane fraction of the cell, and in the postribosomal supernatant. Our results suggest that the VSV glycoprotein is synthesized exclusively on membrane polyribosomes, while at least some of the M, N, and NS proteins are made on free polyribosomes.
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PMID:Site of synthesis of membrane and nonmembrane proteins of vesicular stomatitis virus. 16 63

The poliovirus replication complex was isolated and purified from infected HeLa S3 cells. Preparations with RNA-dependent RNA polymerase activity were concentrated 200- and 1000-fold with respect to the original virus and total protein content. The enzyme activity was found to be associated with the proteins NCVPI, 2, 3, 4, (5), 6 and VPl/NCVPx. The structural proteins VP2, 3 and 4 were not present. Addition of cycloheximide to infected cells resulted in a decrease in the in vitro polymerase activity and a loss in NCVPI content. Treatment of the infected cells with toloylsulphonyl-phenylalanine chloromethyl ketone (TPCK) and iodoacetamide (IAA) led to an inhibition of in vivo RNA synthesis. The 750 g supernatant fluids obtained from extracts of these cells were able to block RNA synthesis in vitro. Electrophoretic profiles of the respective protein compositions indicate that large virus precursor proteins are responsible for the inhibition of poliovirus RNA synthesis in vivo and in vitro.
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PMID:Virus-specific proteins associated with the replication complex of poliovirus RNA. 16 19

Three types of conditional lethal mutant were isolated from wild-type vesicular stomatitis virus, New Jersey serotype, after mutagenization by 5-fluorouracil: (i) conventional temperature-sensitive (ts) mutants, which form plaques at 31 C but not at 39 C; (ii) conventional host range mutants (hr CE), which grow in BHK but not in secondary chicken embryo cells; and (iii) temperature-dependent host range mutants (td CE), which form plaques both at 31 and 39 C on BHK cells but only at 31 C on chicken embryo cells. To determine whether the mutation in hr CE and td CE mutants affected the virion-associated RNA transcriptase, this enzyme was assayed in vitro at 31 and 39 C, and the results were compared with those obtained for the wild-type virus. The RNA trascriptase activity of hr CE mutants did not appear to be affected by the mutation. The td CE mutants fall into two classes: those that synthesized RNA at 39 C similar to the wild-type virus and those that did not. One mutant of the latter category, td CE 3, had heat-sensitive transcriptase regardless of whether it was grown in BHK or chicken embryo cells. A revertant to the wild-type phenotype isolated from this mutant had regained the ability to synthesize RNA at 39 C. These results strongly suggest that a polypeptide that is either the transcriptase itself or part of the transcriptase complex was made temperature sensitive by the mutation in the second class of td CE mutants. The inhibition of the transcriptase activity of the mutant td CE 3 was fully reversible by lowering the temperature of incubation from 39 to 31 C, and both inhibition and reactivation appeared to be instantaneous.
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PMID:Virion trascriptase activity differences in host range mutants of vesicular stomatitis virus. 17 Apr 23

The virion transcriptase (nucleosidetriphosphate: RNA nucleotidyltransferase, EC 2.7.7.6) of vesicular stomatitis virus was fully active when ribonucleoprotein cores from purified virions were added to cell-free protein synthesizing systems of eukaryotic origin. Synthesis of mRNA was linear for at least 3 hr and the newly synthesized viral mRNA was efficiently utilized for the synthesis of viral proteins N (nucleoprotein), NS, and M (matrix); small amounts of a putative G (glycoprotein protein precursor and several unidentified polypeptides were regularly synthesized. The ratio of the various newly synthesized viral proteins was identical after different periods of coupled mRNA and protein synthesis. Identical proteins were obtained when the cell-free protein synthesizing systems were programmed with purified VSV mRNA synthesized in vitro. No detectable L protein was synthesized, even though transcripts complementary to the complete viral genome were detectable in the mRNA preparation by hybridization.
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PMID:Coupled in vitro transcription and translation of vesicular stomatitis virus messenger RNA. 17 Jun 4


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