Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.26.9 (ribonuclease)
 6,589 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hormones play a role in the regulation of gene expression by inducing changes in enzyme patterns in target cells mediated by the synthesis of specific RNA molecules. Erythropoiesis has been used as a system for studying the molecular mechanism of regulation of gene action by means of two hormones: erythropoietin and testosterone. Experiments designed to correlate the biochemical action of both hormones on rat marrow cells are herein reported. Both factors seems to act at different biochemical and citological levels. Erythropoietin triggers the erythropoietic process acting on the erythropoietin sensitive cells (ESC), in which the hormone induces the synthesis of a high molecular weight RNA, which is the precursor of a functional 9 S messenger RNA. Testosterone seems to act on polychromatophilic erythroblasts, in which the synthesis of ribosomal RNA or its precursor is stimulated. The steroid enhances the nuclear ribonuclease activity, which could represent a control mechanism for the processing (maturation) of high molecular weight RNAs. The incorporation of 3H-GTP and 3H-UTP into RNA by isolated rat bone marrow nuclei is stimulated by erythropoietin and testosterone. Using alpha-amanitine and different ionic strength conditions it was found that erythropoietin enhances preferentially RNA polymerase II activity while testosterone increases RNA polymerase I activity. It is postulated that erythropoietin and testosterone act synergically to create the biochemical machinery for hemoglobin synthesis, the macromolecule that characterizes the erythropoietic process.
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PMID:Hormonal control of gene expression: differential activation of rat bone marrow RNA polymerases by erythropoietin and testosterone. 9 87

Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein. Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein. Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation. But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations. Transcription per milligram chromatin DNA was 25-fold higher using E. coli RNA polymerase instead of rat liver RNA polymerase II. The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA. One [lambda32P]UTP nucleotide was incorporated/8 UMP nucleotides. The product obtained was sensitive to ribonuclease treatment. In the presence of ATP, GTP and CTP [lambda-32P]UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188.
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PMID:Transcription of rat liver chromatin by Escherichia coli RNA polymerase: template properties after protein restriction. 36 67

Atypical eukaryotic RNA polymerase activity was demonstrated in nuclei of Crypthecodinium cohnii, a eukaryote devoid of histones. Nuclei were isolated from growing cultures of this dinoflagellate and assayed for endogenous RNA polymerase (EC 2.7.7.6) activity. There was a biphasic response to Mg2+ with optima at approximately 0.01 and 0.02 M MgCl2, but in contrast to other eukaryotic RNA polymerases, this enzyme activity was inhibited by low MnCl2 concentrations. In the presence of 0.01 M MgCL2 the optimum (NH4)2SO4 concentration was 0.025 M, a concentration at which the nuclei were lysed. Incorporation of [3H]UMP into RNA was inhibited by actinomycin D and dependent on the presence of undergraded DNA, and the reaction product was sensitive to ribonuclease and KOH digestion. Omission of one or more ribonucleoside triphosphates greatly reduced the incorporation. Only a slight enhancement of RNA polymerase activity resulted from the addition of various amounts of native and denatured calf thymus DNA. Spermine caused a marked inhibition while spermidine had little effect on RNA synthesis in the nuclei. Under the optimum conditions described in the present paper the nuclei incorporated approximately 3 pmoles of [3H]UMP/microgram DNA at 25 C for 15 min, and approximately 80% of this activity was inhibited by the eukaryotic RNA polymerase II inhibitor, alpha-amanitin (20 micrograms/ml). A unique situation therefore exists in C. cohnii nuclei, in which absence of histones (a prokaryotic trait) is combined with alpha-amanitin-sensitive RNA polymerase activity (a eukaryotic trait).
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PMID:RNA synthesis in isolated nuclei of the dinoflagellate Crypthecodinium cohnii. 57 93

Nuclei of GH3 cells, isolated by detergent lysis, synthesized RNA for an extended period at 29 degrees C in the presence of rat liver ribonuclease inhibitor (RI). Extended RNA synthesis was dependent upon the presence of RI. Sucrose gradient sedimentation analysis of the cell-free reaction products showed that RNAs ranging from 4 S to greater than 28 S were synthesized. Further characterization of the RNA products was made by examining the sensitivity of synthesis to alpha-amanitin and actinomycin D as well as by oligo(dT)-cellulose binding properties. Evidence was obtained that RNA polymerases I, II, and III were functioning in isolated GH3 nuclei. Newly synthesized RNAs were found in both the nuclear pellet and postnuclear supernatant fractions. RNA polymerase I products remained associated with the nuclear pellet throughout a 60-min incubation period whereas RNAs synthesized by RNA polymerase III emerged rapidly into the supernatant fraction. RNA polymerase II products were distributed in both fractions and were found to contain poly(A). De novo poly(A) synthesis was demonstrated and found to be inhibited by cordvcepin triphosphate (3'-dATP). Supernatant RNAs synthesized by polymerase II contained a poly(A) segment of about 150 adenine residues; these transcripts sedimented heterogeneously with an apparent size distribution (under denaturing conditions) which was smaller than that of nuclear RNA polymerase II products and which resembled that of cellular mRNA. Qualitative differences in the nuclear and supernatant RNAs, the kinetics of appearance of the latter, and the differential effect of 3'-dATP on the extranuclear appearance of supernatant RNAs suggest that a process resembling nuclear-cytoplasmic RNA transport occurred in this cell-free nuclear system.
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PMID:Extended RNA synthesis in isolated nuclei from rat pituitary tumor cells. 98 56

A single ip injection of triiodothyronine (T3; 30 mug/100 g BW) to thyroidectomized rats markedly stimulates RNA synthesis in isolated liver nuclei. The increased level of RNA synthesized in vitro by isolated nuclei does not depend on a reduced degradation of the nascent RNA molecules, since ribonuclease activities are not affected by the administration of T3. In addition, our results have confirmed previous findings of Tata et al. that the increase in nucleolar alpha-amanitin-resistant RNA polymerase I activity at low ionic strength always preceded the rise of the nucleoplasmic alpha-amanitin-sensitive RNA polymerase II activity at high ionic strength. Moreover, it has been found that a significant increase in an alpha-amanitin-resistant activity at high ionic strength occurs as early as 10 h after hormone injection. This enzyme, which forms RNA with a U to G ratio significantly higher than that of RNA synthesized by the nucleolar alpha-amanitin-resistant enzyme, is probably nucleoplasmic RNA polymerase III which is though to synthesize 5S and transfer RNAs. The possible role and the mechanism(s) of the early and concomitant increase in nucleolar and nucleoplasmic alpha-aminitin-resistant activities, and of the subsequent rise of RNA polymerase II activity following T3 administration are discussed.
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PMID:Sequential stimulation of nuclear RNA polymerase activities in livers from thyroidectomized rats treated with triiodothyronine. 119 15

Regulation of transcription elongation is an important mechanism in controlling eukaryotic gene expression. SII is an RNA polymerase II-binding protein that stimulates transcription elongation and also activates nascent transcript cleavage by RNA polymerase II in elongation complexes in vitro (Reines, D. (1992) J. Biol. Chem. 267, 3795-3800). Here we show that SII-dependent in vitro transcription through an arrest site in a human gene is preceded by nascent transcript cleavage. RNA cleavage appeared to be an obligatory step in the SII activation process. Recombinant SII activated cleavage while a truncated derivative lacking polymerase binding activity did not. Cleavage was not restricted to an elongation complex arrested at this particular site, showing that nascent RNA hydrolysis is a general property of RNA polymerase II elongation complexes. These data support a model whereby SII stimulates elongation via a ribonuclease activity of the elongation complex.
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PMID:The RNA polymerase II elongation complex. Factor-dependent transcription elongation involves nascent RNA cleavage. 137 32

Glucocorticoid-induced muscle atrophy is associated with a decrease in the level of protein synthesis and a loss of RNA. This paper reports the behaviour of RNA polymerase I- and RNA polymerase II-directed transcription (EC 2.7.7.6) in nuclei isolated from skeletal muscles of rats given a catabolic dose of dexamethasone acetate (5 mg per Kg body weight) over a period of 4 days. Both activities were altered by the dexamethasone treatment. In the case of RNA polymerase I-mediated transcription there was a loss of template-engaged enzymes indicating the existence of an inhibition of initiation of transcription while the rate of elongation of bound enzymes was unaltered. The number of RNA polymerase II-chromatin bound enzymes was increased, but the mean polynucleotide elongation rate was reduced. The possibility that glucocorticoids may impair the elongation stage of transcription in skeletal muscle by increasing the frequency of premature termination of transcripts is discussed. No evidence was obtained for any increase in ribonuclease activity in muscle nuclei of dexamethasone-treated animals.
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PMID:Glucocorticoid-mediated muscle atrophy: alterations in transcriptional activity of skeletal muscle nuclei. 193 39

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

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

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


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