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 increase of the contour length of the low molecular linear duplex DNA in the complex with an alkaloid sanguinarine has been evidenced by the viscometric method. The enzymatic hydrolysis of modified DNA by pancreatic deoxyribonuclease I and RNA synthesis of DNA by rat liver nuclear RNA polymerase were studied. Sanguinarine has been shown to inhibit the first stages of DNA hydrolysis. This alkaloid is a weaker inhibitor than ethidium bromide, a more potent inhibitor than actinomycin D and exerts an inhibiting effect similar to that of distamycin A. Sanguinarine also decreases the rate of the labelled precursor incorporation into the acid-insoluble fractions by nuclear RNA polymerase from rat liver. A 50% inhibition by sanguinarine was observed at the same alkaloid concentration as that of ethidium bromide.
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PMID:[Inhibition of the reactions of DNA hydrolysis and RNA synthesis by the alkaloid sanguinarine]. 620 Nov 96

The interconversion between the right (R) and left (L) helical forms of poly[d(G-C)] occurs at low concentrations of MgCl2 and EtOH, acting together in a highly synergistic manner. Thus, the cooperative R---L transition is induced by only 0.4 mM and 4 MM MgCl2 in combination with 20% and 10% EtOH, respectively. The L form of poly[d(G-C)] formed under these conditions has the spectroscopic properties (absorption, circular dichroism) previously demonstrated under high salt conditions (Pohl and Jovin, 1972) and thought to correspond to the left-handed Z DNA structures recently established by X-ray crystallography (Wang et al., 1979; Drew et al., 1980). However, L DNA formed in Mg2+-EtOH (which we designate as Z* DNA) has unique properties: a) it can be sedimented readily out of solution at low speed, indicative of condensation and intermolecular aggregation; b) it supports the binding of several intercalating (ethidium bromide, actinomycin D) and non-intercalating (mithramycin) drugs, although these interact preferentially with the R (i.e., B) form of DNA; and c) it functions as a template for Escherichia coli RNA polymerase. B and Z* DNAs can be generated under identical ionic conditions and compared in a number of biochemical systems. Our results suggest that left-handed DNA may form under physiological conditions and serve a biological function.
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PMID:Z* DNA, the left-handed helical form of poly[d(G-C)] in MgCl2-ethanol, is biologically active. 623 31

The primary structure of the E. coli rpoC gene (5321 base pairs) coding the beta'-subunit of RNA polymerase as well as its adjacent segment have been determined. The structure analysis of the peptides obtained by cleavage of the protein with cyanogen bromide and trypsin has confirmed the amino acid sequence of the beta'-subunit deduced from the nucleotide sequence analysis. The beta'-subunit of E. coli RNA polymerase contains 1407 amino acid residues. Its translation is initiated by codon GUG and terminated by codon TAA. It has been detected that the sequence following the terminating codon is strikingly homologous to known sequences of rho-independent terminators.
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PMID:The primary structure of E. coli RNA polymerase, Nucleotide sequence of the rpoC gene and amino acid sequence of the beta'-subunit. 628 30

The cleavable dinucleotide photoaffinity probe 5'-[[(4-azidophenacyl)thio]phosphoryl]adenylyl(3'-5')uridine was prepared and used to determine the 5' contacts of a trinucleotide in an Escherichia coli RNA polymerase/T7 DNA transcription complex. The probe was prepared by alkylating 5'-(thiophosphoryl)adenylyl(3'-5')uridine with azidophenacyl bromide. The 5'-(thiophosphorylyl(3'-5')uridine was prepared by the abortive initiation reaction of RNA polymerase on a poly[d(A-T)] DNA template, using adenosine 5'-O-(thiomonophosphate) and uridine triphosphate as substrates. A transcription complex containing a radiolabeled trinucleotide at the A1 promoter of bacteriophage T7 D111 or D123 DNA was prepared by using the dinucleotide photoaffinity probe as initiator and cytidine [alpha-32P]triphosphate as the other substrate. After photolysis, the labeled subunits and DNA were isolated, and the trinucleotide was removed in the presence of phenylmercuric acetate and analyzed by polyacrylamide gel electrophoresis. The 5' end of the trinucleotide was found to label the DNA (approximately 88%) and also the beta (approximately 10%) and sigma (approximately 3%) subunits of E. coli RNA polymerase. It was also shown that the order of migration of the beta and beta' subunits of E. coli RNA polymerase on polyacrylamide gel electrophoresis in sodium dodecyl sulfate is different from that in sodium dodecyl sulfate plus urea.
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PMID:Synthesis of a cleavable dinucleotide photoaffinity probe of ribonucleic acid polymerase: application to trinucleotide labeling of an Escherichia coli transcription complex. 635 6

The "killer" plasmid and a larger double-stranded RNA plasmid of yeast exist in intracellular virion particles. Purification of these particles from a diploid killer strain of yeast (grown into stationary growth on ethanol) resulted in co-purification of a DNA-independent RNA polymerase activity. This activity incorporates and requires all four ribonucleoside triphosphates and will not act on deoxyribonucleoside triphosphates. The reaction requires magnesium, is inhibited by sulfhydryl-oxidizing reagents and high concentrations of monovalent cation, but is insensitive to DNase, alpha-amanitin, and actinomycin D. Pyrophosphate inhibits the reaction as does ethidium bromide. Exogenous nucleic acids have no effect on the reaction. The product is mostly single-stranded RNA, some of which is released from the enzymatically active virions.
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PMID:Virion DNA-independent RNA polymerase from Saccharomyces cerevisiae. 700 33

The mechanism of inhibition of RNA polymerase-catalyzed synthesis of RNA by actinomycin D and the phenan-thridinium derivatives ethidium bromide and 3,8-diamino-6-ethylphenanthridinium bromide (DEMB) is examined. A general kinetic equation describing the dependence of RNA synthesis on DNA template concentration is derived and distinct expressions corresponding to various possible mechanisms of inhibition are subsequently obtained by introducing into the equations assumptions as appropriate for the individual mechanisms. The fitting of the experimental results of inhibition into the resulting equations suggested that the ethidium bromide and DEMB inhibit RNA polymerase by forming an inhibitor-template complex which interferes with enzyme recognition of, and binding to, appropriate sites on the template (binding inhibition). The fitting of the dependence of the rate of RNA synthesis on the bound-inhibitor to DNA ratios to the derived kinetic expressions also allows a tentative distinction to be made as to whether ethidium bromide and DEMB interfere with RNA synthesis by a mechanism of 'partial' or 'complete' inhibition.
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PMID:A kinetic study on the mechanism of inhibition of RNA synthesis catalyzed by DNA-dependent RNA polymerase. Differences in inhibition by ethidium bromide, 3,8-diamino-6-ethylphenanthridinium bromide and actinomycin d. 702 10

The preparation and characterization of a protein from wheat germ showing strong affinity to amatoxins (ABP) but differing from RNA polymerase B (II) is described. The purification, traced by [3H]amatoxin (O-methyldehydroxymethyl-alpha-amanitin), comprises 4 chromatographic steps, on Biogel A 1.5, DEAE-Sephadex, phosphocellulose, and again Biogel A 1.5. The protein exhibited in dodecyl sulfate polyacrylamide gel electrophoresis one single band with a molecular mass of 29,000 Da. Its isoelectric point is 4.9. The dissociation constant of the complex ABP-[3H]amatoxin is KD20 = 5 X 10(-7)M as determined by equilibrium dialysis against alpha-amanitin. By cyanogen bromide the protein is split into two fragments with molecular masses of 22,000 and 7,000 Da, respectively whose amino acid analyses, on summation, give the amino acid composition of ABP.
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PMID:[Isolation and characterization of an amatoxin-binding protein from wheat germ (author's transl)]. 707 28

Hedamycin forms a stable complex with DNA and introduces alkali labile linkages in the DNA. These labile linkages are located at deoxyguanosine residues and are cleaved by the treatment used for breakage at bases alkylated by dimethyl sulfate. The reaction of hedamycin with all G residues in the chain is not uniform, and certain positions, particularily those in TG tracts, are especially reactive. The reaction of hedamycin with DNA can be inhibited by ethidium bromide, suggesting that intercalation is important in positioning the reactive group of hedamycin near to the base which is modified. The low amount of hedamycin needed to produce observable breakage, its specificity for reaction with DNA and its ability to react with DNA under mild conditions make it suitable for use as a probe of protein-DNA complexes. This was shown by the ability of lac repressor and RNA polymerase to block reaction of hedamycin with the DNA of the lac regulatory region.
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PMID:Formation of alkali labile linkages in DNA by hedamycin and use of hedamycin as a probe of protein-DNA complexes. 713 91

Catalyzed polymerization reactions represent a primary anabolic activity of all cells. It can be assumed that early cells carried out such reactions, in which macromolecular catalysts were encapsulated within some type of boundary membrane. In the experiments described here, we show that a template-independent RNA polymerase (polynucleotide phosphorylase) can be encapsulated in dimyristoyl phosphatidylcholine vesicles without substrate. When the substrate adenosine diphosphate (ADP) was provided externally, long-chain RNA polymers were synthesized within the vesicles. Substrate flux was maximized by maintaining the vesicles at the phase transition temperature of the component lipid. A protease was introduced externally as an additional control. Free enzyme was inactivated under identical conditions. RNA products were visualized in situ by ethidium bromide fluorescence. The products were harvested from the liposomes, radiolabeled, and analyzed by polyacrylamide gel electrophoresis. Encapsulated catalysts represent a model for primitive cellular systems in which an RNA polymerase was entrapped within a protected microenvironment.
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PMID:Production of RNA by a polymerase protein encapsulated within phospholipid vesicles. 752 10

Little knowledge of DNA replication in cyanobacteria is available. In this study, we report the development and characterization of an in vitro system for studies of replication of the endogenous plasmids from the unicellular cyanobacterium Synechocystis 6803. This system (fraction III) was isolated at high salt concentrations and partially purified on a heparin-agarose column. DNA polymerases in Synechocystis 6803 appeared to be associated with membranes and could be released by the addition of ammonium sulfate to 20% saturation. DNA synthesis in fraction III was dependent on the addition of cyanobacterial plasmids isolated from the same strain. The in vitro replication products consist mostly of the supercoiled form of the plasmids. Unlike replication of many Escherichia coli plasmids, replication of cyanobacterial plasmids did not require added ATP, was not inhibited by omission of the ribonucleotides, and was insensitive to the RNA polymerase inhibitor rifampicin and the gyrase inhibitor novobiocin, but was inhibited by ethidium bromide. These data suggest that RNA may not be involved in the initiation of replication of cyanobacterial plasmids from Synechocystis 6803. In addition, intermediates of replication have been detected by two-dimensional gel electrophoresis. Density labeling experiments also indicate that cyanobacterial plasmid synthesis in vitro occurs by a semiconservative replication.
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PMID:In vitro replication of cyanobacterial plasmids from Synechocystis PCC 6803. 753 50


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