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)

Isolated rat liver nuclei were incubated under conditions when RNA polymerase I or RNA polymerase II was preferentially active. It was shown that [gamma-32P] ATP and [gamma-32P] GTP were incorporated into phenol extractable, TCA-precipitable material. RNase, actinomycin D, heparin and, in the case of RNA-polymerase II, alpha-amanitine inhibited precursor incorporation. These data are interpreted as evidence in favour of the initiation of RNA synthesis in isolated rat liver nuclei.
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PMID:[Initiation of RNA synthesis in isolated rat liver nuclei]. 258 May 66

A differentiation-competent mouse muscle cell line containing 50-100-times the diploid number of dihydrofolate reductase (DHFR) genes was used to study regulation of DHFR mRNA levels during myogenic withdrawal from the cell cycle. Quantitative RNase protection assays showed DHFR mRNA levels decreased 15-fold during commitment; DHFR pre-mRNA levels decreased 7-fold. Concomitantly, transcription products were analyzed by hybridization to Southern blots of dhfr-containing plasmids. Control run-on assays performed on nonamplified parental cells indicated that run-on signals measured in amplified cells were dhfr amplicon-specific. Run-on signals were sensitive to alpha-amanitin, indicating RNA polymerase 2 specificity, and did not hybridize to pBR322 sequences, demonstrating hybridization stringency. Comparison of run-on signals hybridizing to DNA fragments representing either the 5' end of the gene or the entire gene showed that transcriptional repression occurred within the first 660 bases of the 30-kilobase gene, consistent with regulation at the level of either initiation or early pretermination. In contrast to the DHFR gene, DNA 5' to all but the first few bases of the DHFR coding region (between -1000 and +60 base pairs from the preferred cap site) showed strong run-on transcription in both proliferative and committed cells. Northern blot analysis using a probe complementary both to the dhfr coding region and the upstream region showed a uniform decrease in all detectable transcripts. No commitment-dependent changes in dhfr cap site usage, splicing, or polyadenylylation site usage were detected. Our results support a transcriptional model for regulation of DHFR mRNA levels.
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PMID:Transcriptional repression of the mouse dihydrofolate reductase gene during muscle cell commitment. 259 72

An in vitro transcription system was developed from H411EC3 (H4) hepatoma cells, which mimics the in vivo up-regulation by glucocorticoid hormones on ribosomal RNA (rRNA) synthesis. Ribosomal DNA (rDNA) transcription in extracts derived from H4 cells grown in the presence of 100 nM triamcinolone acetonide was 4- to 5-fold greater than that in extracts derived from cells grown in the absence of glucocorticoid. This effect was not a general stimulation by the steroid, as RNA polymerase II transcription of the metallothionein-1 gene which lacked a glucocorticoid responsive element was unaffected. The increased transcription in hormone-treated extracts was also independent of differential ribonuclease activities or inhibitors as ascertained by the inclusion of ribonuclease inhibitor and mixing experiments, respectively. Chromatography of H4 cell extracts on heparin-sepharose followed by transcription complementation analysis, showed that the hormone-induced stimulatory activity eluted with the fraction (TFIA) which contains RNA polymerase I (Pol I). Immunoblot analysis with specific anti-Pol I antibody showed similar subunit profiles in the absence and presence of the hormone. The presence of a Pol I enhancer element in addition to the rDNA promoter did not further modify the glucocorticoid-induced transcription. These results indicate that the glucocorticoid-mediated effects could be observed in cell extracts which accurately initiate transcription of cloned rat rDNA. Moreover, the alterations of rDNA transcription by the hormone is effected by a factor which elutes with fraction TFIA.
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PMID:Glucocorticoid-induced stimulation of ribosomal gene transcription in rat hepatoma cells is mediated by modification of RNA polymerase I or an associated factor. 260 60

We used a ribonuclease cleavage assay to screen for insulin receptor mRNA sequence alterations in 12 patients with syndromes of severe insulin resistance. Uniformly labeled [32P]antisense RNA probes complementary to insulin receptor mRNA were prepared by an SP6 or T7 RNA polymerase transcription reaction. Four probes ranging in size from 670-1470 bases were used to examine the entire 4.2-kilobase receptor protein-coding region. Patient RNA samples were hybridized to individual probes in solution, and mismatched sequences were detected by susceptibility to cleavage by a mixture of RNAses A and T1. The method was validated with insulin receptor mRNAs from cells transfected with cDNA constructs bearing known point and deletion mutations. Alterations in the insulin receptor mRNA sequence of two patients were detected. A patient with the type A syndrome of severe insulin resistance (A2-Boston) had a mutation in the insulin receptor beta-subunit mRNA sequence that localized to the region coding for amino acid residues 1174-1211 near the tyrosine kinase domain. The second alteration was a sequence polymorphism in the insulin receptor alpha-subunit mRNA in a patient with lipoatropic diabetes (LA-2) that localized to a region within amino acids 268-272. Direct sequence analysis revealed that the ribonuclease cleavage sites in patients A2-Boston and LA-2 were due to distinct single base changes in the insulin receptor gene and mRNA. Additional insulin receptor mRNA sequence polymorphisms were also identified as mismatches between the labeled RNA probes used and mRNA from several cultured human cell types. This study demonstrates that ribonuclease cleavage can rapidly detect and localize insulin receptor mRNA sequence mutations and polymorphic variations as small as single base changes. Further analysis of insulin receptor mRNA sequence alterations identified in this way may elucidate a possible genetic basis for functional insulin receptor defects in patients with severe insulin resistance and can also reveal some insulin receptor sequence polymorphisms that occur in the population at large.
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PMID:Insulin receptor messenger ribonucleic acid sequence alterations detected by ribonuclease cleavage in patients with syndromes of insulin resistance. 273 94

Even when neutralized by saturating amounts of monoclonal IgG directed against the haemagglutinin, influenza virus attaches to cells with kinetics similar to those of infectious virus. It then enters those cells and is uncoated; its RNA becomes localized within the nucleus and its lipid envelope and associated proteins remain in the cytoplasm. In this report we show that despite the apparent normality of these early stages of virus-cell interaction, neutralized virus underwent no detectable primary transcription. In contrast, there was only a slight inhibition of transcription by neutralized virus in vitro which was insufficient to account for the loss in infectivity, despite using mRNA to measure the production of capped oligonucleotides or to prime the elongation step. To test whether the absence of primary transcription in vivo resulted from non-accessibility of the genome rather than an effect on the transcriptase complex itself, we examined the susceptibility to RNase of virion RNA after inoculation of cells with neutralized virus. Data clearly show that, unlike RNA of infectious virus, RNA of neutralized virus did not become sensitive to RNase and we conclude that neutralization of influenza virus by IgG results in failure of virus to undergo a secondary uncoating process which is necessary for the activity of the virion transcriptase complex. Finally we show that by treatment of virions in vitro with detergent it is possible to produce a core structure which is stable and has some of the properties expected of a structure resulting from primary uncoating.
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PMID:IgG-neutralized influenza virus undergoes primary, but not secondary uncoating in vivo. 276 31

Transcription termination in vitro by vaccinia RNA polymerase is dependent on a trans-acting factor, VTF, that is associated with, if not identical to, the vaccinia mRNA capping enzyme. VTF-induced termination occurs approximately 50 nucleotides downstream of a signal sequence TTTTTNT in the non-transcribed templated strand; thus the cognate sequence UUUUUNU is expressed in the nascent RNA. To address the role of the nascent RNA in chain termination, the effects of nucleotide base analog substitutions were studied. Incorporation of bromo- (Br) UMP or iodo- (I) UMP into RNA abrogated factor-dependent termination without preventing the synthesis of read-through transcripts. Substitution of either ITP or 7'-methylguanosine for GTP did not inhibit factor-dependent termination, nor did the substitution of BrCTP or ICTP for CTP. The early transcripts synthesized in vitro were sensitive to RNase T2 but resistant to RNase H, indicating an absence of extensive hybridization of RNA product to the DNA template. Substitution of BrUTP for UTP did not alter the nuclease sensitivity of the transcripts, suggesting that increased stability of RNA:DNA hybrid structures did not account for the analog effects. These results are consistent with a model in which recognition of the primary sequence UUUUUNU in nascent RNA by the polymerase and/or VTF is required for transcription termination.
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PMID:Factor-dependent transcription termination by vaccinia virus RNA polymerase. Evidence that the cis-acting termination signal is in nascent RNA. 283 68

I have previously reported an activity in HeLa cells which facilitates transcript displacement by purified mammalian RNA polymerase II in vitro. I have shown that this activity copurifies with one of two separable ribonuclease (RNase) H activities in HeLa cells. The RNase H activity in question has characteristics similar to those reported for RNase H2b from calf thymus. RNase H proteins purified from several other sources including Escherichia coli also show renaturase activity. When the renaturase/RNase H protein is present during transcription by purified RNA polymerase II, transcripts are truncated close to the 5' end, and the remainder of the transcript is displaced normally from its template by the polymerase. Since RNA polymerase II dependent transcripts in vivo normally require the presence of the 5'-triphosphate terminus for capping, the in vivo significance of RNase H as a renaturase factor is presently not understood. However, the in vitro action of renaturase/RNase H suggests that the mechanism of this reaction may involve R-loop displacement after formation of a short single-stranded region of DNA on the template strand following hydrolysis of a hybrid transcript oligonucleotide by RNase H.
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PMID:Renaturase and ribonuclease H: a novel mechanism that influences transcript displacement by RNA polymerase II in vitro. 283 25

A solution hybridisation assay has been developed which allows the quantitation of specific viral (RNA) sequences in infected cells. The assay makes use of single-stranded (ss) RNA probes of known polarity synthesised at high specific activity in vitro from cDNA clones of the relevant viral gene by the SP6 or T7 RNA polymerase. These probes are used together with samples containing the RNA to be detected at a known concentration to construct a calibration curve to relate RNase resistant radioactivity following solution hybridisation to amount of RNA. The amount of RNA in experimental samples is then determined using the calibration curve that is produced each time the assay is performed. The UKtc strain of Rotavirus growing in BSC-1 cells was used to develop this method but with the substitution of suitable cDNA clones it could be applied to any viral system.
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PMID:A rapid and sensitive solution hybridisation assay for the quantitative determination of specific viral RNA sequences. 285 3

The leader RNA transcript of vesicular stomatitis virus inhibits transcription of the adenovirus major late promoter and virus-associated genes in a soluble HeLa cell transcription system. We examined the specific nucleotide sequence involved and the potential role of leader-protein interactions in this inhibition of RNA polymerase II- and III-directed transcription. Using synthetic oligodeoxynucleotides homologous to regions of the leader RNA molecule, we extend our previous results (B.W. Grinnell and R.R. Wagner, Cell 36:533-543, 1984) that suggest a role for the AU-rich region of the leader RNA or the homologous AT region of a cloned cDNA leader in the inhibition of DNA-dependent transcription. Our results indicate that a short nucleotide sequence (AUUAUUA) or its deoxynucleotide homolog (ATTATTA) appears to be the minimal requirement for the leader RNA to inhibit transcription by both RNA polymerases, but sequences flanking both sides of this region increase the inhibitory activity. Nucleotide changes in the homologous AT-rich region drastically decrease the transcriptional inhibitory activity. Leader RNAs from wild-type virus, but not from a 5'-defective interfering particle, form a ribonuclease-resistant, protease-sensitive ribonucleoprotein complex in the soluble HeLa cell extract. Several lines of evidence suggest that the leader RNA specifically interacts with a 65,000-dalton (65K) cellular protein. In a fractionated cell extract, only those fractions containing this 65K protein could reverse the inhibition of DNA-dependent RNA synthesis by the plus-strand vesicular stomatitis virus leader RNA or by homologous DNA. In studies with synthetic oligodeoxynucleotides homologous to leader RNA sequences, only those oligonucleotides containing the inhibitory sequence were able to bind to a gradient fraction containing the 65K protein.
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PMID:Inhibition of DNA-dependent transcription by the leader RNA of vesicular stomatitis virus: role of specific nucleotide sequences and cell protein binding. 301 5

We devised a strategy to measure the efficiency of transcription termination in vivo by RNA polymerase on polyomavirus DNA. Pulse-labeled nuclear RNA was hybridized with a single-stranded polyomavirus DNA fragment which spans the transcription initiation region. Hybrids were treated with RNase, bound to nitrocellulose filters, eluted with S1 nuclease, and analyzed by gel electrophoresis. The ratio of full-length to less-than-full-length DNA-RNA hybrids was used to calculate transcription termination frequency. We found that 50% of the polymerases terminated per traverse of the L DNA strand during the late phase of infection. The method for mapping in vivo pulse-labeled RNAs which we developed is potentially useful for studying unstable cellular or viral RNAs.
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PMID:Use of a novel S1 nuclease RNA-mapping technique to measure efficiency of transcription termination on polyomavirus DNA. 302 98


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