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:3.1.27.1 (RNase)
16,360 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

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

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

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

We have cloned and determined the nucleotide (nt) sequence of a 6.5-kb genomic DNA fragment containing the rat MyoD gene (encoding a muscle regulatory factor, MyoD). Mouse fibroblasts transfected with this DNA display a high degree of conversion to a muscle phenotype, suggesting that this genomic clone contains sufficient sequence information to allow the production of the rat MyoD protein in these cells. The 6.5-kb genomic fragment contains the complete coding region of MyoD, distributed over three exons, plus 2.3 kb of 5'-noncoding sequence and 1.4 kb of 3'-noncoding sequence. Based on RNase protection assays, the major transcription start point of MyoD is located 210 nt 5' to a methionine start codon and 26 nt 3' to a TAAATA motif which bears similarity to a consensus recognition sequence (TATA) utilized by eukaryotic RNA polymerase II transcription complexes. The high degree of identity between the amino acid sequence of rat MyoD and the MyoD proteins isolated from other vertebrates indicates that this muscle regulatory protein has been evolutionarily conserved.
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PMID:Isolation and structural analysis of the rat MyoD gene. 132 78

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

RNase MRP is a site-specific ribonucleoprotein endoribonuclease that cleaves RNA sequence complementary to mammalian mitochondrial origins of replication in a manner consistent with a role in primer RNA metabolism. The same activity in the yeast Saccharomyces cerevisiae has recently been identified; it cleaves an RNA substrate complementary to a yeast mitochondrial origin of replication at an exact site of linkage of RNA to DNA. We have purified this yeast enzyme further and detect a single, novel RNA of 340 nucleotides associated with the enzymatic activity. The single-copy nuclear gene for this RNA was sequenced and mapped to the right arm of chromosome XIV. The identity of the clone, as encoding the RNA copurifying with enzymatic activity, was confirmed by a match to the directly determined sequence of the RNA. The gene sequence also identified a 340-nucleotide RNA in total yeast RNA and in purified RNase MRP enzyme preparations. Inspection of the sequence of the yeast RNA revealed homologies to the RNA component of mouse RNase MRP, 49% overall with specific regions of much greater similarity. The flanking regions of the gene showed characteristics of an RNA polymerase II transcription unit, including a TATAAA box and a 7/8 match to the yeast cell cycle box UAS. The RNase MRP RNA gene was deleted by insertional replacement and found to be essential for cellular viability, indicating a critical nuclear role for RNase MRP.
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PMID:Yeast site-specific ribonucleoprotein endoribonuclease MRP contains an RNA component homologous to mammalian RNase MRP RNA and essential for cell viability. 139 74


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