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)

A DNA-dependent RNA polymerase has been isolated from Caldariella acidophila, a thermophilic bacterium living in acidic hot springs at temperatures ranging from 63 to 89 degrees C. The enzyme was purified 180-fold and is composed of five different subunits having the following molecular weights: a = 127000, b = 120000, c = 72000, d = 65000, and e = 38000. The enzyme is activated by Mn2+ and Mg2+ and exhibits optimal activity in the presence of 0.5 mM Mn2+. The activity depends on ionic strength, with a maximum at 0.25 M KCl, and exhibits a pH optimum at 7.8 in the presence of Tris-HCl buffer. The enzyme shows a high degree of thermophilicity, its temperature optimum being 80 degrees C in the in vitro assay. The thermophilicity of C. acidophila RNA polymerase allows studies on enzyme-template interactions to be performed in a temperature range where many templates are close to their Tm.
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PMID:DNA-dependent RNA polymerase from the thermophilic bacterium Caldariella acidophila. Purification and basic properties of the enzyme. 0 9

The properties of poly(G) polymerase and poly(A) polymerase activities in the DNA-dependent RNA polymerase [nucleosidetriphosphate: RNA nucleotidyltransferase EC 2.7.7.6] I fraction from cauliflower (Brassica oleracea var. botrytis) were comparatively investigated. The pH optimum, the effect of ionic strength, the effect of substrate concentration on the rate of synthesis, the effect of divalent metal ion concentration, and the time course of synthesis at different temperatures were all different for the three polymerase activities. The enzyme fraction preferentially utilized denatured DNA. Synthetic poly(C) and poly(U) were more effectively utillized for the synthesis of polyguanylate and polyadenylate, respectively. Further, it was found that poly(G) and poly(A) formed in vitro by the enzyme fraction had chain length of 25-28 and 84-89 nucleotides, respectively, and that poly (adenylate-gluanylate) chain was hardly formed when ATP and GTP were added together as substrates in the same reaction medium.
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PMID:Comparative studies on polyguanylate polymerase and polyadenylate polymerase activities in the DNA-dependent RNA polymerase I fraction from cauliflower. 0 54

Purified preparations of molluscum contagiosum virus contain a DNA-dependent RNA polymerase (EC 2.7.7.6) with similar but not identical properties to those of the enzyme found in vaccinia virions. The ultraviolet inactivation kinetics of the RNA polymerase from both viruses were similar, displaying fast and slow components. Ultraviolet irradiation destroyed the interfering capacities of molluscum and inactivated vaccinia virions, and the interferon-inducing capacity of molluscum virus slowly and with first-order kinetics. Inactivation studies of the interferon-inducing capacity of vaccinia virus were complicated by cytotoxic effects. Electron microscopical studies showed all stages of virus growth in vaccinia-infected mouse embryo cells; molluscum virus appeared to be degraded in lysosome-like bodies. In preliminary studies, marked changes in cytoplasmic RNA synthesis and in patterns of polypeptide synthesis were found in vaccinia-infected but not in molluscum-infected mouse embryo cells.
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PMID:Molluscum contagiosum -- a defective poxvirus? 1 Dec 75

Studies on the effects of substrates on RNA polymerase I [EC 2.7.7.6] in vitro showed that nucleolar RNA synthesis was inhibited by an excess of substrate nucleoside triphosphates in the presence of Mg2+. GTP and UTP were more inhibitory than CTP and ATP. These compounds specfically inhibited nucleolar RNA synthesis and a concentration of GTP that strongly inhibited nucleolar RNA synthesis did not inhibit RNA synthesis by partially purified RNA polymerase I. The inhibition of nucleolar RNA synthesis disappeared at pH 9.0 without any change in the apparent Km for GTP or the Vmax of RNA synthesis.
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PMID:Inhibitory effects of nucleoside triphosphates on nucleolar RNA synthesis. 3 1

RNA polymerase was extracted from the Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV)-induced C3H/He mouse ascites sarcoma cells (SR-C3H). RNA polymerase was separated into RNA polymerases I and II by DEAE-Sephadex chromatography. RNA polymerase I was separated into Ia and Ib fractions by phospho-cellulose chromatography. In SR-C3H cells RNA polymerase Ib was the main component of RNA polymerase I. At 0.05--0.1 M ammonium sulphate RNA polymerase I transcribed native DNA most actively, and RNA polymerase II transcribed denatured DNA most actively. Partial digestion of DNA by DNAase I enhanced RNA synthesis by RNA polymerases I and II. At ionic strength over 0.2 M ammonium sulphate, the initiation reaction of RNA polymerases I and II was inhibited. The initiation complexes of RNA polymerases I and II with native DNA were more stable against high salt concentration than with denatured DNA.
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PMID:Characterization of RNA polymerases from Rous sarcoma virus-induced mouse ascites sarcoma cells. 3 35

9-O-methyloximd erythromycin A and its analogue inhibited reverse transcriptase and blocked focus formation of Rous sarcoma virus. These chemicals inhibited neither DNA-dependent DNA polymerase nor DNA-dependent RNA polymerase from bacterial sources. However, they inhibited reverse transcriptase with an apparently differnt mechanism than that by rifamycin ABDP.
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PMID:Oxime derivatives of erythromycin: inhibitors of Rous sarcoma virus reverse transcriptase activity and focus formation. 4 82

The proportion of cells absorbing trypan blue (tb-+ character) can be used to measure the late c.p.e. of wild-type poliovirus (ts-+. tb-+), which was the same at restrictive (39-2 to 39-6 degrees C) or permissive (37 degrees C) temperatures. Of twenty ts mutants, seven showed normal c.p.e. at 37 degrees C but were defective in C.P.E. (TB) AT 39-5 degrees C; all seven tb mutants have previously been shown (Cooper et al. 1971) to give evidence of a primary defect in replicase 1 activity (to make the complementary or minus strand of virus RNA). The remainder (tb-+) have all previously been shown to give evidence of a primary defect either in replicase II activity (to make progeny plus strands) or in structural protein. Thus, the late c.p.e. is dependent on a product of the replicase I gene, of which the in vivo effector is probably double-stranded RNA. Late c.p.e. is not caused by prevention of host protein, RNA or DNA synthesis and is not necessarily correlated with lysosomal enzyme release. The tb mutants were also defective in inducing early changes in chromatin (chr) and in prevention of thymidine incorporation (pti), but the tb and pti/chr characters are probably independent expressions of replicase I activity. Virus growth does not depend on repression of DNA synthesis. Poliovirus represses the activities of host DNA-dependent RNA polymerase I and II to an equal extent. There is no evidence that repression of DNA or RNA synthesis results from direct interaction of virus protein with the DNA.
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PMID:Poliovirus temperature-sensitivie mutants defective in cytopathic effects are also defective in synthesis of double-stranded RNA. 4 94

1. Rifamazine (AF/RP) a dimeric rifamycin, is active against bacterial DNA-dependent RNA polymerase and against viral RNA-dependent DNA polymerase. 2. Rifamazine is active also against DNA-dependent RNA polymerase extracted from rifampicin-resistant mutants of Escherichia coli. It does not interfere with enzyme-template interaction or with RNA elongation. It blocks initiation. 3. A comparison is made between the mechanism of action of rifamazine and that of rifampicin, and of AF/013 (octyloxime of 3-formylrifamycin SV), a C-class rifamycin. Our results show that the mechanism of action of rifamazine is more similar to that of rifampicin than to that of the octyloxime derivative. 4. Activity of rifamazine against RNA polymerase from rifampicin-resistant mutants is thought to be due to binding of the dimer to both the rifamycin-specific binding site and to a second weak site.
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PMID:Mechanism of action of rifamazine, a member of a new class of (dimeric) rifamycins. 5 95

Two forms of DNA-dependent RNA polymerase have been partially purified (about 100-fold relative to the crude extract) from 48-h old cells of Streptomyces antibioticus. The two forms show different Mg2+ optima for the incorporation of [3H]UMP into RNA. Substances inhibiting transcription have been isolated by ammonium sulfate precipitation from one of the fractions produced during the polymerase purification. Actinomycin can be shown to inhibit RNA synthesis catalyzed by the S. antibioticus polymerases to a similar extent regardless of the template used. When S. antibioticus DNA is the template, actinomycin inhibits transcription by S. antibioticus polymerase to a degree that is significantly less than the observed actinomycin inhibition of synthesis catalyzed by Escherichia coli polymerase or by either S. antibioticus or E. coli polymerase with calf thymus DNA as the template. Using an assay previously developed, it was shown that the association constant for the binding of actinomycin to S. antibioticus DNA was increased by the presence of RNA polymerase in the binding mixture, while the association constant for the binding to calf thymus DNA was decreased by RNA polymerase. RNA synthesis in crude, cell-free extracts of 12-h old S. antibioticus cells (not producing actinomycin) is less refractory to actinomycin inhibition than synthesis catalyzed by extracts of 48-h old (actinomycin producing) cells, and both extracts catalyze appreciable RNA synthesis at actinomycin concentrations that completely inhibit RNA synthesis catalyzed by E. coli extracts.
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PMID:RNA synthesis in Streptomyces antibioticus: in vitro effects of actinomycin and transcriptional inhibitors from 48-h cells. 6 Jan 28

The sulfated glycosaminoglycans chondroitin 4-sulfate, chondroitin 6-sulfate, keratan sulfate, dermatan sulfate, heparin, and glycosaminoglycan polysulfate are competitive inhibitors of the DNA-dependent RNA polymerase, the DNA-dependent RNA polymerase and the RNA-dependent DNA polymerase (reverse transcriptase). The unsulfated glycosaminoglycans chondroitin and hyaluronate are without any influence on the synthesis of DNA and RNA. The strongest inhibitor is a glycosaminoglycan polysulfate with four sulfate groups per disaccharide unit. It has the following inhibitor constants: DNA polymerase, Ki = 1.5 X 10(-6) M; RNA polymerase, Ki = 0.9 X 10(-6) M; reverse transcriptase, Ki = 1.1 X 10(-6) M. The inhibition is closely correlated to the degree of sulfation of the glycosaminoglycans. There is a relationship between the sulfate/hexosamine ratio and the degree of inhibition. The inhibition of the DNA and RNA synthesizing enzymes by sulfated glycosaminoglycans depends on the nature of the template. With double-stranded DNA as template, inhibition occurs only when sulfated glycosaminoglycans are added before or shortly after (30 s) initiation of the synthesis. There is no inhibition if the inhibitors are added after the onset of the synthesis. On the other hand, with a single-stranded template synthesis was blocked completely at each phase of reaction.
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PMID:Interactions of glycosaminoglycans with DNA and RNA synthesizing enzymes in vitro. 6 Nov 58


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