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 5'-cap-containing leader sequence of the most abundant 19S and 16S mRNAs of simian virus 40 (SV40) was previously mapped between 0.67 and 0.76 map units. We now find that the two late mRNA species contain multiple 5' ends. Eight different RNase T2-resistant cap structures were identified:m7GpppmAmpU (47%); m7GpppmAmpUmpU (19%); m7GpppmAmpC (16%); m7GpppmAmpCmpA (5%); m7GpppmAmpG (6%); m7GpppGmpC (3%); m7GpppmAmGmpA (2%); m7GpppGmpCmpG (2%). Capped T1 oligonucleotides of 19S and 16S mRNAs have been isolated by two different procedures: (i) chromatography on a DEAE-cellulose column followed by paper electrophoresis and (ii) two-dimensional electrophoresis/homochromatography. Cap structures of the isolated 5' oligonucleotides were identified. Each of the major caps was found to be associated with a few differential 5' oligonucleotides, implying a vast heterogeneity at the termini of SV40 late mRNAs. The results suggest that on SV40 DNA, RNA polymerase II has a reportoire of initiation points. In most of the cases, initiation takes place with adenosine triphosphate followed by a pyrimidine. Alternatively, transcription may start at one specific point but a unique mechanism of processing generates heterogeneous populations of termini with a common 5' adenosine triphosphate.
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PMID:Sequence heterogeneity at the 5' termini of late simian virus 40 19S and 16S mRNAs. 22 54

The participation of host RNA polymerase II in the vaccinia life cycle was examined by comparing efficiency of multiplication after treating the Ama+ sensitive and Ama 102 drug resistant lines with alpha-amanitin. In the latter, resistance is due to a mutation in RNA polymerase II. The toxin profoundly reduces synthesis of virus-specified polypeptides and morphopoeisis in Ama+ but not in Ama 102 rat myoblasts without appreciably altering vaccinia DNA replication in either cell type. This implicates RNA polymerase II in the expression of late virus functions. Circumstantial evidence from a model system indicates that gamma irradiation of the host prior to infection might disrupt transcription into functional mRNA from the nucleus. Irradiation does not, however, alter the capability of the host to support vaccinia multiplication fully. Therefore, ongoing host nuclear transcription may not be required by this virus. The above results are consistent with the ability of cytoplasts to produce small quantities of mature progeny. Our studies lead us to hypothesize that RNA polymerase II or a subunit of the host enzyme may participate directly in late transcription of the vaccinia genome.
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PMID:Biogenesis of poxviruses: role for the DNA-dependent RNA polymerase II of the host during expression of late functions. 22 96

Simian Virus (SV40) transcriptional intermediates (T.I.) were isolated from infected cell nuclei incubated in vitro in the presence of the four ribonucleoside triphosphates. The nascent mRNA strands in the viral DNA-RNA hybrid molecules were hydrogen bonded to their template by 200-250 nucleotides on the average, as judged from the extent of their RNase resistance and the aspect of T.I. under electron microscope after treatment with 50 per cent formamide. The RNA polymerase involved (RNA polymerase II) synthesized up to full length transcripts at a rate of approximately 150 nucleotides/min. at 25 degrees C. Each SV40 infected cell was found to contain about 200 active T.I. molecules at the peak of late transcription. The DNA in the T.I. molecules was exclusively form I DNA only in cell infected with the tsA30 mutant of SV40 that had been transferred to non-permissive temperature in order to arrest DNA replication, but both form I DNA and molecules behaving as replicative intermediates (R.I.) in wild type infected cells.
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PMID:Characterization of simian virus 40 transcriptional intermediates in infected CV1 cell nuclei. 23 Aug 57

Chromatin isolated from immature oocytes was found to contain an endogenous RNA polymerase activity (RNA nucleotidyltransferase; nucleoside triphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) that synthesizes predominately 5S RNA. However, the levels of total RNA synthesis and 5S RNA synthesis in chromatin were each stimulated 10- to 50-fold by an exogenous RNA polymerase III purified from X. laevis oocytes. The 5S genes in chromatin were transcribed by the exogenous enzyme in a highly selective (3000-fold above random) and predominately asymmetric fashion. A significant fraction of 5S RNA sequences were also found in a discrete transcript, approximately 5S in size. Total RNA synthesis was significantly stimulated when chromatin was transcribed by oocyte RNA polymerase I, murine RNA polymerase II, and low levels of Escherichia coli RNA polymerase. However, these enzymes did not significantly stimulate 5S RNA synthesis above the endogenous levels. Both homologous oocyte RNA polymerase I and III and E. coli RNA polymerase transcribed the 5S genes in deproteinized DNA to approximately the same extent (severalfold above random) and both the sense and anti-sense strands of the gene were transcribed. It appears, therefore, that both chromatin-associated components and a purified RNA polymerase III are necessary and sufficient for the selective and accurate transcription of the 5S RNA genes in vitro.
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PMID:Selective and accurate transcription of the Xenopus laevis 5S RNA genes in isolated chromatin by purified RNA polymerase III. 26 93

RNA synthesis in isolated HeLa cell nuclei prepared from cells pretreated with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) is inhibited in a time-dependent manner. After 40-min pretreatment of cells with 60 muM DRB in the presence of actinomycin D (0.04 mug/ml), the rate of RNA synthesis in isolated nuclei, measured by [(3)H]UTP incorporation, is decreased by 63%. The DRB-resistant one-third of heterogeneous nuclear is distributed over the entire size range of heterogeneous nuclear RNA with some enrichment in the 18S range, as was observed earlier by pulse-labeling whole cells. A subclass of nucleoplasmic RNA molecules is defined in the approximate size range 110 to 250 x 10(3) daltons (330-740 nucleotides). By using heparin (2 mg/ml) to block the synthesis of smaller RNA, a peak in the chain-length range 330-740 nucleotides can be clearly resolved on 2.2% polyacrylamide/1% agarose gels in nuclei from control and DRB-treated cells. The synthesis of these molecules is largely ( approximately 90%) resistant to DRB but sensitive to alpha-amanitin at 1 mug/ml. The in vitro synthesis of molecules in the 140-330 residue range is also sensitive to alpha-amanitin at 1 mug/ml, and it is not at all affected by pretreatment of cells with DRB. Although the synthesis of the RNA in both the 330-740 and the 140-330 residue size ranges appears to be catalyzed by RNA polymerase II, the results with heparin suggest that there may be reinitiation of molecules in the 140-330 size range but not in the 330-740 range in vitro. The synthesis of 4.5S RNA ( approximately 100 nucleotides) and 5S RNA (120 nucleotides) is unaffected by pretreatment of cells with DRB and, as previously reported, is catalyzed by RNA polymerase III, with reinitiation occurring in vitro. Addition of DRB directly to isolated HeLa cell nuclei in vitro has no detectable effect on the overall rate of RNA synthesis.
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PMID:Definition of subclasses of nucleoplasmic RNA. 27 Jul 36

Mutant Chinese hamster ovary cell lines temperature-sensitive (TS) for growth and containing TS mutations in RNA polymerase II (nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2.7.7.6) have been isolated. Wild-type cells were treated with the mutagen N-methyl-N'-nitro-N-nitrosoguanidine and a population of cells possessing mutations in RNA polymerase II was initially selected by isolating alpha-amanitin-resistant clones at 34 degrees . Of 168 such alpha-amanitin-resistant isolates screened for temperature sensitivity, nine were TS for growth at 39.5 degrees . By examining the behavior of the alpha-amanitin resistance of these TS cell lines in somatic cell hybrids, the TS mutation in a number of them was shown to be in RNA polymerase II. Hybrid cells obtained by the fusion of the TS and alpha-amanitin-resistant cells with cells possessing alpha-amanitin-sensitive polymerase II grew at both 34 degrees and 39.5 degrees ; the TS mutations were recessive. At 34 degrees all the hybrids were alpha-amanitin-resistant and possessed a mixture of alpha-amanitin-resistant and sensitive polymerase II. At 39.5 degrees the alpha-amanitin-resistant polymerase II activities in hybrids of four of the TS cell lines were lost; these four lines were alpha-amanitin-sensitive and possessed only alpha-amanitin-sensitive polymerase II. Temperature-insensitive revertants of two of these mutants were isolated. Reversion of the TS phenotype for mutants TsAma(R)-1 and TsAma(R)-8 was accompanied by an alteration in the level of alpha-amanitin resistance of the RNA polymerase II activities in the revertant cells. Together these data provide convincing evidence that TS mutations in RNA polymerase II can be coselected with alpha-amanitin resistance.
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PMID:Temperature-sensitive RNA polymerase II mutations in Chinese hamster ovary cells. 27 57

Nascent RNA molecules were labeled in vivo and elongated in vitro by incubation of the isolated nuclei in the presence of mercurated nucleotides. The RNA molecules initiated and labeled in vivo and elongated in vitro were then selectively purified on a thiopropyl 6-B Sepharose affinity column. The procedure was shown to be free of artifacts since the addition of mercurated nucleotides and the retention on the affinity column is mediated by the endogenous RNA polymerase II (nucleoside triphosphate:RNA nucleotidyltransferase; EC 2.7.7.6), is sensitive to actinomycin D, and is dependent on the presence of all four ribonucleotide triphosphates. This general procedure was applied to the mapping of viral promoters late after adenovirus 2 infection of HeLa cells. RNA purified as described above was hybridized to restriction enzyme fragments attached to nitrocellulose filters. The 5' ends of the nascent RNA chains are located in coordinates 9.5-17 for a rightward transcript, 0-25 for a leftward transcript, and possibly 60-70 for a second rightward transcript. These locations clearly differ from locations of the early promoters and therefore suggest that the transition from early to late functions is controlled at the transcriptional level.
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PMID:Mapping of adenovirus late promoters with nascent mercurated RNA. 27 97

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

Because influenza viral RNA transcription in vitro is greatly enhanced by the addition of a primer dinucleotide, ApG or GpG, we have proposed that viral RNA transcription in vivo requires initiation by primer RNAs synthesized by the host cell, specifically by RNA polymerase II, thereby explaining the alpha-amanitin sensitivity of viral RNA transcription in vivo. Here, we identify such primer RNAs, initially in reticulocyte extracts, where they are shown to be globin mRNAs. Purified globin mRNAs very effectively stimulated viral RNA transcription in vitro, and the resulting transcripts directed the synthesis of all the nonglycosylated virus-specific proteins in micrococcal nuclease-treated L cell extracts. The viral RNA transcripts synthesized in vitro primed by ApG also directed the synthesis of the nonglycosylated virus-specific proteins, but the globin mRNA-primed transcripts were translated about 3 times more efficiently. The translation of the globin mRNA-primed, but not the ApG-primed, viral RNA transcripts was inhibited by 7-methylguanosine 5'-phosphate in the presence of S-adenosylhomocysteine, suggesting that the globin mRNA-primed transcripts contained a 5'-terminal methylated cap structure. We propose that this cap was transferred from the globin mRNA primer to the newly synthesized viral RNA transcripts, because no detectable de novo synthesis of a methylated cap occurred during globin mRNA-primed viral RNA transcription. Preliminary experiments indicate that other purified eukaryotic mRNAs also stimulate influenza viral RNA transcription in vitro.
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PMID:Globin mRNAs are primers for the transcription of influenza viral RNA in vitro. 28 99

The steatogenic effect on the liver of Rifampicin, a potent inhibitor of the DNA-dependent RNA polymerase in bacteria, was investigated in male and female rats which received either 200 mg or 400 mg of Rifampicin/kg/24 h for 8 days. The determination of total lipids (TL), triglycerides (TG), total cholesterol (TC) and phospholipids (PL) showed a significant increase of TL, TG and TC in the liver at a dose of 400 mg. There was better reproducibility in the male whose blood TG and PL were significantly decreased. These results showed that fatty liver can be induced by very high doses of Rifampicin in rats. A blockage of the very low density lipoproteins (VLDL) biosynthesis and/or secretion can be expected. As a potent steatogenic toxin, alpha-amanitin, is a strong inhibitor of RNA polymerase II in eukariotic cells, a relationship between the RNA polymerase inhibition induced by both of substances and a subsequent inhibition of the biosynthesis of the protein moiety of lipoproteins can be considered. Nevertheless Rifampicin is at present not considered as an inhibitor in eukariotic cells and it will be of great interest to test such a possibility with the high doses used in these experiments, in further work.
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PMID:Fatty liver induced by high doses of rifampicin in the rat: possible relation with an inhibition of RNA polymerases in eukariotic cells. 28 41


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