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:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The formation of reovirus double-stranded (ds) RNA and of oligo adenylic acid (oligo A) is inhibited by 5 mug of actinomycin D per ml added at the time of viral infection. Viral proteins are synthesized and assembled into dsRNA-deficient particles under these conditions. The addition of cycloheximide to infected cells during the mid-logarithmic phase of viral replication terminates protein and dsRNA synthesis, but allows continued oligo A synthesis for about 1 h. The (3)H-labeled oligo A formed in the presence of cycloheximide is incorporated into particles whose density in CsCl is identical to that of reovirions. Using the large particulate or virus factory-containing cytoplasmic fraction of infected L-cells, we have established an in vitro system for the synthesis of oligo A. The in vitro product migrates slightly faster in sodium dodecyl sulfate acrylamide gels than marker oligo A. Oligo A synthesis in vitro continues for about 1 h, requires, the presence of only one ribonucleoside triphosphate (ATP), is not inhibited by DNase or RNase, but is abruptly terminated by the addition of chymotrypsin to the reaction mixture. Oligo A formed both in vivo and in vitro is released from the factory fraction by chymotrypsin digestion. The enzymes which catalyze the synthesis of oligo A, dsRNA, and single-stranded RNA all exhibit a similar temperature dependence with an optimum of approximately 45 C. These results indicate that oligo A is formed within the core of the nascent virion after the completion of dsRNA synthesis; they suggest that the oligo A polymerase is an alternative activity of the virion-bound transcriptase and that it is regulated by outer capsomere proteins.
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PMID:Shythesis of reovirus oligo adenylic acid in vivo and in vitro. 485 7

Amino acid starvation of "stringent RNA control" (RC(str)) strains of Escherichia coli (E. coli) results in the cessation of net protein and net RNA synthesis, whereas "relaxed RNA control" (RC(rel)) strains continue net RNA synthesis under the same conditions of amino acid starvation. This report tests further the hypothesis that net RNA synthesis is markedly reduced during amino acid starvation of RC(str) strains as a result of reduction in the supply of substrates of the RNA polymerase. Bacterial ribonucleoside triphosphate pool levels were measured before and after the arrest of protein synthesis in RC(str) and RC(rel) strains. Protein synthesis was inhibited either by addition of trimethoprim to the medium or by the use of a mutant having a temperature-sensitive valyl-tRNA synthetase. The ribonucleoside triphosphate pool levels do not decline significantly during inhibition of protein synthesis in RC(str) strains under either condition, and there is no apparent correlation between the measured pool levels and the residual rate of net RNA synthesis in RC(str) and RC(rel) strains. Thus, these data argue against the hypothesis that the regulation of RNA synthesis is mediated by the availability of substrates of the RNA polymerase.
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PMID:Nucleoside triphosphate pools and the regulation of RNA synthesis in E. coli. 489 29

1. Crude extracts of the extreme halophile Halobacterium cutirubrum contain separable DNA-dependent and RNA-dependent RNA polymerases. 2. The RNA-dependent enzyme has been purified about 2800-fold. 3. It requires RNA, preferably of high molecular weight, and all four ribonucleoside triphosphates to incorporate (14)C-labelled nucleoside triphosphate into an acid-insoluble, ribonuclease-sensitive product. 4. Both the stability and activity of the RNA polymerase are relatively insensitive to changes in potassium chloride or sodium chloride concentration, but incorporation is stimulated by both Mg(2+) and Mn(2+). 5. The molecular weight of the enzyme is about 17000-18000.
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PMID:Nucleic acid enzymology of extremely halophilic bacteria. Halobacterium cutirubrum ribonucleic acid-dependent ribonucleic acid polymerase. 511 74

Subviral particles containing reovirus RNA transcriptase have been isolated from extracts of virus-infected mouse fibroblast cells. The purified particles which lacked the outer protein capsomeres of the mature virion had a buoyant density of 1.43-1.44 g/ml in CsCl and contained all of the double-stranded RNA genome of the intact virus. The particles were free of nuclease activity. RNA synthesis required all four ribonucleoside triphosphates and was dependent on magnesium or manganese; optimal activity required potassium or ammonium ions. In the presence of a ribonucleoside triphosphate regenerating system, reaction rates were linear for 20 hr. RNA yields of 40-fold in excess of input template could be obtained. Completed RNA chains were released from the subviral particles. In the course of RNA synthesis, the double-stranded RNA template was fully conserved. The RNA products formed in vitro displayed profiles in sucrose gradients similar to those found for in vitro reovirus mRNA. The RNA products were single-stranded and did not self-anneal. Over 90 percent of the transcriptase products could be annealed with template double-stranded RNA. The annealed products migrated in acrylamide gels as double-stranded RNA, indicating efficient in vitro transcription.
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PMID:Properties of RNA transcriptase in reovirus subviral particles. 526 50

A procedure is described for isolation in a soluble form of a ribonucleic acid polymerase from rat testes. Evidence is presented that this enzyme catalyzes three distinct reactions: (a) deoxyribonucleic acid-directed synthesis of RNA in the presence of all four major ribonucleoside triphosphates; (b) DNA-primed formation of polyadenylic acid and other ribohomopolymers in the presence of single ribonucleoside triphosphate substrates; (c) synthesis of complementary polyribonucleotides in the presence of various ribohomopolymer primers. The properties of these reactions are discussed with respect to metal ion requirements, affinities for ribonucleoside triphosphates and primer polynucleotides, heat denaturation of DNA primers, and the effects of ionic strength, beta-mercaptoethanol, polyamines, temperature, and inhibitors on the rates and extent of the reactions. The testicular ribonucleic acid polymerase is a very unstable enzyme that can be stabilized by high concentrations of glycerol.
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PMID:Isolation and properties of a testicular ribonucleic acid polymerase. 531 60

Luzzati, Denise (Institut de Biologie Physico-Chimique, Paris, France). Effect of thymine starvation on messenger ribonucleic acid synthesis in Escherichia coli. J. Bacteriol. 92:1435-1446. 1966.-During the course of thymine starvation, the rate of synthesis of messenger ribonucleic acid (mRNA, the rapidly labeled fraction of the RNA which decays in the presence of dinitrophenol or which hybridizes with deoxyribonucleic acid) decreases exponentially, in parallel with the viability of the thymine-starved bacteria. The ability of cell-free extracts of starved bacteria to incorporate ribonucleoside triphosphates into RNA was determined; it was found to be inferior to that of extracts from control cells. The analysis of the properties of cell-free extracts of starved cells shows that their decreased RNA polymerase activity is the consequence of a modification of their deoxyribonucleic acid, the ability of which to serve as a template for RNA polymerase decreases during starvation.
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PMID:Effect of thymine starvation on messenger ribonucleic acid synthesis in Escherichia coli. 533 2

Preparations of purified and disrupted suspensions of Coxiella burnetii are able to incorporate ribonucleotides into polymers in the presence of adenosine, guanosine, cytidine, and uridine triphosphates. Nucleotide incorporation requires the presence of all four ribonucleoside triphosphates. The reaction is enhanced by the addition of phosphoenolpyruvate and pyruvic kinase, and exogenous deoxyribonucleic acid, and is inhibited by deoxyribonuclease and actinomycin D. Incorporation is maximal between pH 7.0 and 8.0, and at 37 C. The synthesized polymer is relatively insensitive to deoxyribonuclease and is sensitive to ribonuclease and dilute alkaline hydrolysis. The data indicate the presence of an autonomous deoxyribonucleic acid-dependent ribonucleic acid polymerase in the rickettsial agent.
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PMID:Physiology of rickettsiae. VI. Host-independent synthesis of polyribonucleotides by Coxiella burnetii. 602 13

The characteristics of human rotavirus-associated RNA polymerase activity have been examined in relation to the effects of ribonucleoside triphosphate analogs and S-adenosylmethionine. These effects were analyzed by testing two forms of activated virus particles: EDTA- and heat-treated virions. The former lack outer shell proteins, and activation by means of heat treatment does not introduce any apparent modification in virion structure. Virus-associated RNA polymerase shows similar properties in both preparations, suggesting that outer proteins are not directly involved in RNA synthesis. Transcription in this virus is specifically dependent on a hydrolyzable form of ATP. Such a requirement is not overcome by preincubation or by the addition of S-adenosylmethionine, suggesting a hypothetical mechanism that couples transcription to ATP hydrolysis. The addition of S-adenosylmethionine stimulated transcription and diminished the Km value not only for ATP but also for the other three ribonucleoside triphosphates. Analysis of methylated RNA products suggested that methyl groups were incorporated into all of the RNA species synthesized by virion-associated polymerase. Further analysis of those RNA molecules showed that they contained cap structures at the 5' end. The results suggest that the cap structure at the end of RNA molecules may enable RNA polymerase to elongate transcripts more efficiently, in a reaction in which the hydrolysis of ATP is involved.
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PMID:Effect of S-adenosylmethionine on human rotavirus RNA synthesis. 609 Jun 96

The extent of productive RNA chain initiation in vitro by Escherichia coli RNA polymerase holoenzyme from the bacteriophage T7 A1 and A2 promoters on purified T7 DNA templates has been investigated at very low concentrations of the ribonucleoside triphosphate substrates. As the concentration of ribonucleoside triphosphates in the reaction is decreased from 10 to 1 micro M, the extent of productive RNA chain initiation at these promoter sites drops precipitously at about 3 micro M. At 1 micro M substrate concentration, productive chain initiation from the A1 promoter does not occur even after extended incubation although the dinucleoside tetraphosphate pppApU is produced at a significant rate under these conditions. The reason for the inability of RNA polymerase to carry out productive RNA chain initiation at 1 micro M substrate concentration is not yet understood. The phenomenon is not due to substrate consumption, enzyme inactivation, or a requirement for a nucleoside triphosphatase activity in the reaction. The possibility is raised that there are additional nucleoside triphosphate binding sites on E. coli RNA polymerase which play some role in the process of productive RNA chain initiation.
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PMID:The effect of low substrate concentrations on the extent of productive RNA chain initiation from T7 promoters A1 and A2 by Escherichia coli RNA polymerase. 615 92

RNA polymerase molecules pause at a single site during in vitro transcription of the tryptophan (trp) operon leader region. Pausing was observed when DNA templates derived from Escherichia coli. Salmonella typhimurium, and Klebsiella aerogenes were used. Fingerprint analyses showed that the major RNA species produced by the transcriptional pause is 91 nucleotides long. A minor RNA species 90 nucleotides long was also detected. Single-round transcription experiments were used to study the kinetics of pausing. Time course, pulse-chase, and delayed-labeling experiments suggest that every RNA polymerase molecule transcribing the trp leader region pauses. A suboptimal ribonucleoside triphosphate concentrations, the half-life of paused-leader RNA was approximately 3 min at 22 degrees C and 0.7 min at 37 degrees C. At near-optimal ribonucleoside triphosphate concentrations, the half-time of the paused species dropped to about 0.3 min at 22 degrees C. The appearance and half-life of the paused species were unaffected by salt concentration, rho factor, guanosine 3'-5'-bis(diphosphate), or point mutations in the trp attenuator region. It is postulated that transcriptional pausing may play a role in maintaining the synchronization of transcription and translation that is vital in the control of transcription termination at the trp operon attenuator.
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PMID:Pausing of RNA polymerase during in vitro transcription of the tryptophan operon leader region. 616 81


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