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)

PR toxin, a mycotoxin synthesized by Penicillium roqueforti, impairs the transcriptional process in liver cells; the two main RNA polymerase systems (enzymes A and B) are affected by PR toxin. The toxin does not require an enzymic conversion before interfering with in vitro RNA synthesis. Addition of ammonium sulphate completely prevents the inhibition of transcription by PR toxin. In vitro results, using RNA polymerase purified from E. coli, suggest that PR toxin impairs the activity of the RNA polymerase itself. Regarding the step of the transcription process affected, it is shown that PR toxin inhibits both initiation and elongation of the polynucleotide chain.
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PMID:Mechanism of the inhibition of transcription by PR toxin, a mycotoxin from Penicillium roqueforti. 18 92

Cellular RNA synthesis was studied in mouse L-929 cells and in these cells infected with mengovirus. RNA polymerases I, II, and III were partially purified and their chromatographic properties were analyzed by DEAE-Sephadex A-25 chromatography. RNA polymerase II was purified from mouse liver and its subunit structure was compared to that of normal and virus-infected L-929 cells by two-dimensional gel electrophoresis. By these criteria, the enzymes from all three sources were identical. The RNA synthetic activities and capacities of chromatins from normal and virus-infected cells were compared under a variety of conditions. The endogenous activity in chromatin from infected cells was inhibited relative to controls but the residual activity responded normally to stimulation by ammonium sulfate, heparin, and Sarkosyl. The template capacity of the chromatins was compared with added RNA polymerase II and by a rifampicin challenge assay utilizing Escherichia coli RNA polymerase. Identical results were obtained in each case. The number of growing RNA chains and the rates of their elongations were determined. The results showed that nuclei and chromatin from infected cells have a smaller number of RNA polymerase II molecules engaged in RNA synthesis than normal cells do but that the active molecules elongate RNA chains at the same rate.
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PMID:Cellular RNA synthesis in normal and mengovirus-infected L-929 cells. 20 39

Examinations were made on substances that enhance or inhibit the induction of hepatoma in rats previously fed 3'-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) for a brief period. The substances tested were stilbene, 4-nitrostilbene, 4,4'-dihydroxystilbene, diethylstilbestrol, 17beta-estradiol, and methyltestosterone. Male Donryu rats were fed 0.5 g of 3'-Me-DAB by being maintained on a diet containing 0.06% 3'-Me-DAB, and then they were fed 0.25 or 0.5 g of a test substance with the basal diet. Comparison of the development and yield of hepatomas indicated that 4-nitrostilbene and methyltestosterone had an activity of enhancing 3'-Me-DAB carcinogenesis, whereas diethylstilbestrol and 17beta-estradiol had an activity to retard it. Other substances showed no such activities. The enhancement by 4-nitrostilbene and inhibition by diethylstilbestrol of 3'-Me-DAB carcinogenesis was correlated with their effect on liver nucleic acid metabolism. Feeding of 4-nitrostilbene caused a selective inhibition of Mn2+-(NH4)2SO4-activated RNA polymerase activity of liver nuclei and reduced liver RNA content. The deleterious alteration of liver RNA metabolism was followed by the enhancement in the incorporation of ip-injected 3H-thymidine into DNA of liver nuclei. On the other hand, feeding of diethylstilbestrol increased tissue RNA content without effect on RNA polymerase activity of liver nuclei, and had an activity of increasing the incorporation of 3H-thymidine into DNA. The possible implication of these results with regard to the enhancement and inhibition of hepatocarcinogenesis is discussed.
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PMID:Enhancing and inhibitory effects of some stilbene and steroid compounds on induction of hepatoma in rats fed 3'-methyl-4-(dimethylamino)azobenzene. 20 6

The length of double-stranded coliphage lambda DNA, as determined by electron microscopy using the benzyldimethylalkyl ammonium chloride technique, depends on the mode of dehydration. The freeze-dried DNA form is the longest (16.5 micron), whereas dehydration in methanol (15.9 micron) or in ethanol (three forms: 15.2 micron, 13.9 micron, and 12.4 micron) results in progressively shorter molecules. These measured lengths of the freeze-dried, methanol-dehydrated, and shortest ethanol-dehydrated forms correspond to the axial rise per nucleotide pair in the B, C, and A forms of DNA, respectively. The remaining forms of ethanol-dehydrated DNA seem to represent novel intermediary conformations of DNA. In agreement with the predicted increment, DNA exposed to ethidium bromide and freeze-dried is elongated by 39% (22.9 micron). All size classes show the same relative distribution pattern of bound Escherichia coli RNA polymerase molecules (nucleoside triphosphate:RNA nucleotidyltransferase, EC2.7.7.6), used as intramolecular markers, indicating that the dehydration-caused transitions are uniform.
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PMID:Discrete length classes of DNA depend on mode of dehydration. 27 34

It has been shown that RNA synthesis in isolated hepatopancreas nuclei from Mytilus galloprovincialis is catalyzed by three DNA-dependent RNA polymerases (I, II and III) which resemble those identified in nuclei from mammalian cells. RNA polymerase I is active at 50 mM (NH4)2SO4, catalyzes the synthesis of GMP-rich ribosomal-like RNA and is completely resistant to the toadstool toxin alpha-amanitin. RNA polymerase II and III are active at higher (NH4)2SO4 concentrations, catalyze the synthesis of DNA-like RNA and are inhibited by very low (0.5-1 microgram/ml) and high (200 microgram/ml) concentrations of alpha-amanitin, respectively. Hepatopancreas nuclei retain considerable RNAase activity. Nuclear RNA polymerase activity may be underestimated since a part of the synthetized RNA is degraded.
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PMID:DNA-dependent RNA polymerase activities in hepatopancreas nuclei from Mytilus galloprovincialis Lamarck. 27 40

The stimulatory mechanism of RNA synthesis of calf-thymus chromatin by nuclear 4.5 S RNA from the homologous tissue was investigated by using exogenously added Escherichia coli RNA polymerase. The RNA synthesis was initiated at low concentration of salt, and then the chain elongation was achieved at high concentration of ammonium sulfate in the presence of polyvinyl sulfate. Under these conditions the number of binding sites of RNA polymerase on chromatin which were capable of initiating RNA chain was increased by the addition of the 4.5 S RNA. This stimulation was presumed to result from the release of template restriction in chromatin. The polyvinyl salt minimized ribonuclease activity without changing the RNA polymerase activity bound to the template. Neither rearrangement nor release of chromatin proteins affected the amount or size of RNA produced. Preliminary analysis suggested that the molecular species of RNA produced upon the addition of the 4.5 S RNA from various tissues seemed to be heterologous.
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PMID:Release of template restriction in chromatin by nuclear 4.5s RNA. 32 18

In a medium containing 10mM Tris, pH 8, 10 mM MG++, 50 mM K+ and 10 mM NH4, the binding of an E. coli RNA polymerase holoenzyme unwinds the DNA helix by about 240 degrees at 37 degrees C. In this medium the total unwinding of the DNA increases linearly with the molar ratio of polymerase to DNA. The number of binding sites at which unwinding can occur is very large. If the K+ concentration is increased at 200 mM, the enzyme binds to only a limited number of sites, and the bound and free enzyme molecules do not exchange at an appreciable rate. The unwinding angle of the DNA per bound enzyme in this high salt medium is measured to be 140 degrees at 37 degrees C. The total unwinding angle for a fixed number of bound polymerase molecules per DNA is strongly temperature dependent, and decreases with decreasing temperature.
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PMID:Physiochemical studies on interactions between DNA and RNA polymerase. Unwinding of the DNA helix by Escherichia coli RNA polymerase. 33 Dec 52

Conditions are described for the replication of exogeneous R6K DNA in an in vitro system prepared from Escherichia coli cells. Replication of plasmid DNA in this system is semiconservative and sensitive to actinomycin D, novobiocin, arabinofuranosyl-CTP,N-ethylmaleimide, and inhibitors of DNA-dependent RNA polymerase. An ammonium sulfate fraction prepared from cells carrying the R6K plasmid is required for replication. A direct role in replication for a plasmid-encoded protein, designated pi, in this fraction is indicated by the inactivity of this fraction when prepared from cells carrying a temperature-sensitive mutant plasmid and the thermolability of this fraction when prepared from cells carrying a partial revertant of the mutant plasmid. This plasmid-encoded protein is necessary for the initiation of R6K DNA replication and functions before or during the formation of nascent RNA in the initiation process. The results of titration assays of this protein using various template DNAs suggest that the protein interacts with the plasmid DNA at the region essential for DNA replication.
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PMID:Requirement of a plasmid-encoded protein for replication in vitro of plasmid R6K. 36 78

The DNA-dependent RNA polymerase I (or A) from the lower eukaryote Aspergillus nidulans has been purified on a large scale to apparent homogeneity by homogenizing the fungal hyphae in liquid nitrogen, extraction of the enzyme at high salt concentration, precipitation of RNA polymerase activity with polymin P (a polyethylene imine), elution of the RNA polymerase from the polymin P precipitate, ammonium sulphate precipitation, molecular sieving on Bio-Gel A-1.5m, binding to ion-exchangers and DNA-cellulose affinity chromatography. By this procedure 1.6 mg of RNA polymerase I can be purified over 2000-fold from 500 g wet weight of starting material with a yield of 30--35%. The isolated RNA polymerase I is stable for several months at -20 degrees C. The subunit compostion has been resolved by polyacrylamide gel electrophoresis on two-dimensional gels, using either non-denaturing of 8 M urea (pH 8.7) cylindrical gels in the first dimension and sodium dodecyl sulphate slab gels in the second dimension. The putative subunits have molecular weights of 190,000, 135,000, 63,000, 62,000, 43,000, 29,000, (28,000), 16,000 and probably 13,000 and 12,000. Two distinct forms of RNA polymerase I (Ia and Ib) have been resolved by DEAE-Sephadex A-25 chromatography showing ample differences in enzymatic properties and subunit pattern. Additional information is given on RNA polymerase II (or B) which appears to be highly insensitive to alpha-amanitin at concentrations up to 400 micrograms/ml.
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PMID:RNA polymerase from the fungus, Aspergillus nidulans. Large-scale purification of DNA-dependent RNA polymerase I (or A). 38 Sep 97

DNA-dependent RNA polymerase II (EC 2.7.7.6) from pea seedlings (Pisum sativum var. Alaska) has been purified to homogeneity, as judged by native polyacrylamide electrophoresis. The procedure includes polyethyleneimine precipitation and elution, ammonium sulfate precipitation, DEAE-Sephadex chromatography, phosphocellulose chromatography, and heparin-Sepharose chromatography. The enzyme purified almost to homogeneity has a specific activity of 200 nmol/mg per 15 min at 30 degrees C with denatured calf thymus DNA as template. The enzyme activity is 50% inhibited in the presence of 0.05 migrograms/ml of alpha-amanitin. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate indicates that pea RNA polymerase II is composed of eight subunits with molecular weights and molar ratios (in parentheses) of 170 000 (0.9), 140 000 (1.0), 43 000 (1.5), 26 000 (2.0), 22 500 (1.2), 21 500 (0.6), 18 500 (1.6) and 17 500 (2.3). The structure is closely similar to that of cauliflower RNA polymerase II.
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PMID:Purification and subunit structure of RNA polymerase II from the pea. 49 20


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