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)

Intravenous injection of praseodymium nitrate into female Wistar rats results in liver damage. The aim of this study is to investigate the quality of serum high density lipoprotein content as an index for the severity and time course of liver damage and regeneration following the administration of praseodymium. Serum high density lipoprotein content drastically decreases to a minimum after 24 - 48 h, returning to control values after four days. Liver degeneration is characterized by some intracellular parameters, i.e. the nuclear RNA polymerase reactions, the ribosomal protein synthesis, hepatic spermidine concentration and the activities of serum transaminases (GOT, GPT) and the sorbitdehydrogenase. From the data it is evident that the time course of serum high density lipoprotein content follows the intracellular changes closely. Liver regeneration is represented by the ornithin decarboxylase, the deoxycytidylate deaminase, the thymidine kinase activities and the hepatic putrescine content. The time course of these parameters shows that the regeneration reaches a maximum after 3 - 4 days. In the serum, high density lipoprotein content reflects this process by returning to control values. From our data we conclude that serum high density lipoprotein content after i.v. administration of praseodymium can be considered as an expression of the functional state of the liver.
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PMID:Correlation between serum high density lipoprotein content and liver function during experimental hepatic degeneration and regeneration. 18 75

The fixation of tRNA to Escherichia coli RNA polymerase has been investigated. Bound and free tRNA have been separated and quantified after filtration through cellulose nitrate filters, centrifugation or sucrose gradients or electrophoresis in polyacrylamide gels. We detect no differences between the fixation of E. coli fMet-tRNAfMet, Met-tRNAmMet or uncharged unfractionated tRNA to RNA polymerase. Tight complexes, with a long residence time, are formed between core enzyme and tRNA with a dissociation constant of less than 1 nM. Complexes exist between tRNA and both monomer and dimer forms of the core enzyme. In the monomer complex, one tRNA is bound per alpha 2 beta beta' unit, whereas in the dimer complex only 0.5 tRNA molecule is fixed per alpha 2 beta beta' unit. In contrast to the core enzyme, very little tRNA fixes tightly to the holoenzyme at salt concentrations greater than 80 mM. At lower salt concentrations tRNA fixation results in a loss of sigma subunit from the holo enzyme to the resulting core enzyme where it binds tightly. DNA fixation reduces the binding of tRNA to RNA polymerase and tRNA fixation reduces the binding of DNA. However, binding of DNA to polymerase is not competitive with binding of tRNA, and ternary complexes between RNA polymerase, DNA and tRNA are shown to exist. Our results are discussed in relation to other studies concerning the effects of tRNA upon RNA polymerase.
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PMID:On the binding of tRNA to Escherichia coli RNA polymerase. 38 19

Sodium p-chloromercuribenzoate (PCMB) caused a noticeable reduction of infectivity of prototype strains of type A and Lee strain of type B influenza viruses at concentrations of 100 and 200 mug/ml, respectively, after an incubation at 37 C for 60 min. The virucidal effect on A/AA/2/60 (H2N2) strain was dependent on the concentration of the drug and temperature as well as on the time of incubation. The reagent exerted this effect at a concentration which induced little change in the hemagglutinating and neuraminidase activities of the virus. PCMB inhibited by 50% the virus particle-associated RNA polymerase activity of all prototype strains of type A influenza virus at about 2 mug/ml and that of Lee strain of type B influenza virus at 8.5 mug/ml. Other sulfhydryl reagent such as phenylmercuric nitrate also exhibited virucidal effect on A/AA/2/60 virus which paralleled their inhibition of the virus particle-associated RNA polymerase activity. From these results it was considered likely that the virucidal action of PCMB on influenza viruses was attributable to inhibition of the virus particle-associated RNA polymerase activity.
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PMID:Virucidal effect of sodium p-chloromercuribenzoate on influenza viruses attributable to inhibition of virus particle-associated RNA-dependent RNA polymerase. 116 Feb 1

The effects of mutations in the -10, -35, and Fnr box regions of the narGHJI promoter of Escherichia coli were determined by assaying the expression of beta-galactosidase from narG::lacZ fusion plasmids under aerobic and anaerobic conditions. A 1-base change in the -10 hexamer completely abolished expression, whereas a 3-base change to create the consensus TATAAT resulted in significant aerobic as well as anaerobic expression. A mutation in the putative -35 hexamer did not affect anaerobic expression but reduced aerobic expression from the construction with the -10 consensus sequence. A mutation in the Fnr box severely reduced anaerobic expression but did not affect aerobic expression. When the complete 5' region of the nar operon including the NarL box was present, nitrate stimulated both aerobic and anaerobic expression. Stimulation of expression by nitrate occurred in an fnr mutant but not in a narL mutant. We conclude that the rate of transcription of the nar operon is dependent on two distinct modes of transcription. One mode, which occurs at low levels, depends on the -10 and -35 hexamer sequences and is dramatically enhanced by changing the -10 sequence to the consensus TATAAT. The second depends on the -10 and Fnr box sequences but is independent of the -35 sequence. This second mode occurs at a very high level under anaerobic conditions when Fnr is activated and is also enhanced by changing the -10 sequence to the consensus TATAAT. NarL, activated by nitrate, stimulated both modes of transcription, indicating that it does not act through Fnr but that it directly affects the interaction of RNA polymerase with the promoter.
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PMID:Role of alternative promoter elements in transcription from the nar promoter of Escherichia coli. 173 6

Recognition of -24/-12-type promoters by RNA polymerase requires a special sigma factor, sigma 54 (RpoN NtrA GlnF). In the nitrogen-fixing soybean symbiont Bradyrhizobium japonicum, two functional, highly conserved rpoN genes (rpoN1 and rpoN2) were identified and sequenced. The two predicted B. japonicum RpoN protein sequences were 87% identical, and both showed different levels of homology to the RpoN proteins of other bacteria. Downstream of rpoN2 (but not of rpoN1), two additional open reading frames were identified that corresponded to open reading frames located at similar positions in Klebsiella pneumoniae and Pseudomonas putida. Both B. japonicum rpoN genes complemented the succinate- and nitrate-negative phenotypes of a Rhizobium meliloti rpoN mutant. B. japonicum strains carrying single or double rpoN mutations were still able to utilize C4-dicarboxylates as a carbon source and histidine, proline, or arginine as a nitrogen source, whereas the ability to assimilate nitrate required expression of at least one of the two rpN genes. In symbiosis both rpoN genes could replace each other functionally. The rpoN1/2 double mutant induced about twice as many nodules on soybeans as did the wild type, and these nodules lacked nitrogen fixation activity completely. Transcription of a nifH'-'lacZ fusion was not activated in the rpoN1/2 mutant background, whereas expression of a fixR'-'lacZ fusion in this mutant was affected only marginally. By using rpoN'-'lacZ fusions, rpoN1 expression was shown to be activated at least sevenfold in microaerobiosis as compared with that in aerobiosis, and this type of regulation involved fixLJ. Expression of rpoN2 was observed under all conditions tested and was increased fivefold in an rpoN2 mutant. The data suggested that the rpoN1 gene was regulated in response to oxygen, whereas the rpoN2 gene was negatively autoregulated.
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PMID:Bradyrhizobium japonicum has two differentially regulated, functional homologs of the sigma 54 gene (rpoN). 199 12

Pleiotropic mutants of Alcaligenes eutrophus with the phenotype Hno- have been characterized previously. They are deficient in several diverse metabolic activities, including hydrogen oxidation, nitrate and urea assimilation, denitrification, and various substrate transport systems. Phenotypically similar mutants were identified among hydrogenase-deficient strains of Pseudomonas facilis. The Tn5-labeled hno gene was cloned from a genomic DNA library of A. eutrophus and used to identify the corresponding unimpaired wild-type DNA sequence. The recombinant plasmid pCH148 contained an insert of 12.3 kilobase pairs and was shown to restore the Hno+ phenotype to mutants of A. eutrophus and P. facilis. A cosmid isolated from a DNA library of P. facilis also exhibited intergeneric Hno-complementing activity. The cloned hno loci from both organisms showed DNA homology by Southern blot hybridization. A subclone of pCH148 which contained a 6.5-kilobase-pair insert was constructed. The resulting hybrid, pCH170, not only was able to complement Hno- mutants but also relieved glutamine auxotrophy in NtrA- mutants of enteric bacteria. This suggests that the hno gene product from A. eutrophus is functionally similar to the NtrA protein, which has been identified as a novel sigma factor (sigma 54) of RNA polymerase.
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PMID:An rpoN-like gene of Alcaligenes eutrophus and Pseudomonas facilis controls expression of diverse metabolic pathways, including hydrogen oxidation. 253 72

Hybrid 5' regulatory regions were constructed in which the upstream activator sequence (UAS) and promoter of various nif genes were exchanged with the upstream regulatory sequence (URS) of the fdhF gene from Escherichia coli. They were analysed for their regulatory response under different growth conditions with the aid of fdhF'-'lacZ or nif'-'lacZ fusions. Placement of the UAS from the Bradyrhizobium japonicum nifH gene in front of the spacer (DNA region between URS and promoter) plus promoter from fdhF renders fdhF expression activatable by the Klebsiella pneumoniae NIFA protein, both under aerobic and anaerobic conditions. This excludes the possibility that the spacer of the fdhF5' flanking region contains a site recognized by a putative oxygen- or nitrate-responsive repressor. There was also considerable activation by NIFA of fdhF expression in a construct lacking the nifH UAS but containing the fdhF spacer plus promoter. Further experimental evidence suggests that this reflects a direct interaction between NIFA and RNA polymerase at the ntrA-dependent promoter. A second set of hybrid constructs in which the URS from fdhF (E. coli) was placed in front of the nifD spacer plus promoter from B. japonicum or in front of the K. pneumoniae nifH, nifU, nifB spacers and promoters, delivered inactive constructs in the case of the nifD, nifU and nifB genes. However, a nifH'-'lacZ fusion preceded by its own spacer and promoter plus the foreign fdhF URS displayed all the regulatory characteristics of fdhF expression, i.e. anaerobic induction with formate and repression by oxygen and nitrate. Although it is not known why only one out of the four nif promoters could be activated by the fdhF URS, this result nevertheless demonstrates that the various regulatory stimuli affecting expression of fdhF in E. coli have their target at the upstream regulatory sequence.
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PMID:Construction of chimaeric promoter regions by exchange of the upstream regulatory sequences from fdhF and nif genes. 266 22

Cytological staining with silver nitrate (AgNO3) has proved useful for the localization of nucleoli in interphase nuclei, as well as of nucleolus organizer regions (NORs) in metaphase chromosomes. The affinity of interphase nucleoli and chromosomal NORs to silver is a direct measure of the ongoing transcriptional activity of the rRNA genes or their activity during the preceding interphase, respectively. Correspondingly, human autoantibodies directed against chromatin-associated RNA polymerase I (RPI) should also be of value in the investigation of transcribed rRNA genes. Indirect immunofluorescence using the anti-RPI antibody as a probe has been employed successfully to visualize the chromosomal distribution of NORs in various mammalian species, as well as in human tumor cells. Immunofluorescence staining even permits the identification of heteromorphisms and small aberrations of the chromosomal NORs. The fluorescent intensity of interphase nucleoli is correlated with the different stages of nucleolar activation. In male gametogenesis, RPI-positive granules are present during meiotic prophase up to pachytene, as well as during the early and middle spermatid stages.
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PMID:Immunocytogenetics: localization of transcriptionally active rRNA genes in nucleoli and nucleolus organizer regions by use of human autoantibodies to RNA polymerase I. 305 54

Nitrate reductase, encoded by the nar operon in Escherichia coli, is produced only under anaerobic conditions and induced to its maximum level in the presence of nitrate. The anaerobic expression of the nar operon depends on the fnr gene product (Fnr), and the stimulation of anaerobic expression by nitrate requires the narL gene product (NarL). Distinct regulatory domains within the nar promoter are involved in these two responses. The specific locations of the sequences required for these two regulatory mechanisms were identified by analysis of a detailed set of deletions extending into the regulatory region of the nar operon from the 5' end. A region located around -55 base pairs (bp) from the transcriptional start site and immediately upstream from the presumed RNA polymerase binding site was required for the response to Fnr and anaerobic conditions. A base sequence no longer than 27 bp, located at about -200 bp, was essential for the stimulation by nitrate coupled with NarL. This NarL-specific sequence was equally effective if positioned 10 or 11 bp further upstream or downstream from its wild type position. However, it was ineffective if positioned 4, 6, or 14 bp or greater distances either upstream or downstream. Apparent autoregulation by active nitrate reductase occurred in all 5'-deletion constructions which retained the Fnr response, indicating that this regulatory phenomenon involves sequences located no further than -64 bp from the transcription start site.
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PMID:Location of sequences in the nar promoter of Escherichia coli required for regulation by Fnr and NarL. 313 37

1. Rapidly labelled RNA from Escherichia coli K 12 was characterized by hybridization to denatured E. coli DNA on cellulose nitrate membrane filters. The experiments were designed to show that, if sufficient denatured DNA is offered in a single challenge, practically all the rapidly labelled RNA will hybridize. With the technique employed, 75-80% hybridization efficiency could be obtained as a maximum. Even if an excess of DNA sites were offered, this value could not be improved upon in any single challenge of rapidly labelled RNA with denatured E. coli DNA. 2. It was confirmed that the hybridization technique can separate the rapidly labelled RNA into two fractions. One of these (30% of the total) was efficiently hybridized with the low DNA/RNA ratio (10:1, w/w) used in tests. The other fraction (70% of the total) was hybridized to DNA at low efficiencies with the DNA/RNA ratio 10:1, and was hybridized progressively more effectively as the amount of denatured DNA was increased. A practical maximum of 80% hybridization of all the rapidly labelled RNA was first achieved at a DNA/RNA ratio 210:1 (+/-10:1). This fraction was fully representative of the rapidly labelled RNA with regard to kind and relative amount of materials hybridized. 3. In competition experiments, where additions were made of unlabelled RNA prepared from E. coli DNA, DNA-dependent RNA polymerase (EC 2.7.7.6) and nucleoside 5'-triphosphates, the rapidly labelled RNA fraction hybridized at a low (10:1) DNA/RNA ratio was shown to be competitive with a product from genes other than those responsible for ribosomal RNA synthesis and thus was presumably messenger RNA. At higher DNA/rapidly labelled RNA ratios (200:1), competition with added unlabelled E. coli ribosomal RNA (without messenger RNA contaminants) lowered the hybridization of the rapidly labelled RNA from its 80% maximum to 23%. This proportion of rapidly labelled RNA was not competitive with E. coli ribosomal RNA even when the latter was in large excess. The ribosomal RNA would also not compete with the 23% rapidly labelled RNA bound to DNA at low DNA/RNA ratios. It was thus demonstrated that the major part of E. coli rapidly labelled RNA (70%) is ribosomal RNA, presumably a precursor to the RNA in mature ribosomes. 4. These studies have shown that, when earlier workers used low DNA/RNA ratios (about 10:1) in the assay of messenger RNA in bacterial rapidly labelled RNA, a reasonable estimate of this fraction was achieved. Criticisms that individual messenger RNA species may be synthesized from single DNA sites in E. coli at rates that lead to low efficiencies of messenger RNA binding at low DNA/RNA ratios are refuted. In accordance with earlier results, estimations of the messenger RNA content of E. coli in both rapidly labelled and randomly labelled RNA show that this fraction is 1.8-1.9% of the total RNA. This shows that, if any messenger RNA of relatively long life exists in E. coli, it does not contribute a measurable weight to that of rapidly labelled messenger RNA.
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PMID:Characterization of rapidly labelled ribonucleic acid in Escherichia coli by deoxyribonucleic acid-ribonucleic acid hybridization. 488 72


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