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 stimulatory mechanism of RNA synthesis of calf-thymus chromatin by nuclear 4.5 S RNA from the homologous tissue was investigated by using exogenously added Escherichia coli RNA polymerase. The RNA synthesis was initiated at low concentration of salt, and then the chain elongation was achieved at high concentration of ammonium sulfate in the presence of polyvinyl sulfate. Under these conditions the number of binding sites of RNA polymerase on chromatin which were capable of initiating RNA chain was increased by the addition of the 4.5 S RNA. This stimulation was presumed to result from the release of template restriction in chromatin. The polyvinyl salt minimized ribonuclease activity without changing the RNA polymerase activity bound to the template. Neither rearrangement nor release of chromatin proteins affected the amount or size of RNA produced. Preliminary analysis suggested that the molecular species of RNA produced upon the addition of the 4.5 S RNA from various tissues seemed to be heterologous.
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PMID:Release of template restriction in chromatin by nuclear 4.5s RNA. 32 18

We investigated the ribonucleolytic breakdown of poly(U), poly(A), RNA trascribed from calf thymus DNA with E. coli RNA polymerase, ribosomal RNA, tRNA and mengovirus RNA by an enzyme fraction obrained from a postribosomal supernatant of Ehrlich ascites tumor cells. The single-stranded homopolyribonucleotides are preferentially degraded by the enzyme fraction with the production of ribonucleoside 5'-monophosphates. The RNase activity is completely dependent on the presence of Mg2+ ions and is highest at Mg2+ and K+ concentrations optimal for cell-free protein synthesis. Ribonucleoside 5'-monophosphates, ribonucleoside 2'(3')-monophosphates, ribonucleoside 2'(3'),5'-bisphosphates and transition state analogs consisting of vanadyl sulfate and either ribonucleosides or ribonucleoside 5'-monophosphates in a molar ratio 1:1 inhibit the ribonucleolytic activity of the enzyme fraction. The ribonucleoside 2'(3'),5'-bisphosphates and the transition state analogs are the most effective inhibitors. However, only in the presence of ribonucleoside 2'(3'),5'-bisphosphates a concomitant stimulation by 50 to 60% of poly(U)-directed polyphenylalanine synthesis is observed; all the other RNase inhibitors tested also inhibit polypeptide synthesis. The results of preliminary experiments show that poly(U) and ribonucleoside 2'(3'),5'-bisphosphates are well suited as ligands for affinity chromatography of ribonucleases from Ehrlich ascites tumor cells.
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PMID:Inhibition of ribonucleases by ribonucleotides and transition state analogs in cell-free extracts from Ehrlich ascites tumor cells. 32 84

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

When treated at pH less than 4.5, yeast nuclei or chromatin lose endogenous RNA synthetic activity. This activity is regained by addition of exogenous RNA polymerases. The specificity of transcription in this system by homologous RNA polymerases I and III has been investigated by gel electrophoresis, hybridization analysis, and RNase T1 mapping. Exogenous RNA polymerase I selectively transcribes rRNA genes. The transcription of these genes by polymerase I is 30- and 8-fold more selective than RNA polymerase III and Escherichia coli polymerase holoenzyme, respectively. Exogenous RNA polymerase III synthesized RNAs similar in size to authentic 5 S RNA, 4.5 S pre-tRNA, and 4 S tRNA. Eleven per cent of this RNA is 5 S RNA as determined by hybridization. Neither polymerase I nor E. coli polymerase synthesizes detectable quantities of RNA in this size range. AT1 ribonuclease digestion of 5 S RNA synthesized by exogenous RNA polymerase III acting on acid-treated chromatin gives a fragment pattern corresponding to that of 5 S RNA. Thus, RNA polymerase III transcribes the entire 5 S gene in this system.
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PMID:Specific gene transcription in yeast nuclei and chromatin by added homologous RNA polymerases I and II. 36 64

The diastereomers of uridyl-(3'-5')adenyl-O,O-phosphorothioate [Up(S)A] have been separated by high-performance liquid chromatography. Their identification as RP and SP follows from the RNase A digestion of these products. It was then shown, by the same method, that the R isomer is hydrolyzed by snake venom phosphodiesterase (PDEase) approximately 500 times faster than the S isomer. Similarly, the stereoisomer of adenosine 5'-O-(1-thiotriphosphate) (ATPalphaS), until now arbitrarily designated as isomer B, is hydrolyzed ca 400 times faster by PDEase than is isomer A. From these results it is concluded that the R isomers of Up(S)A and ATPalphaS, isomers B, have the same absolute configuration. It then follows that isomer A of ATPalphaS, the preferred of the two isomers as substrate for DNA-dependent RNA polymerase, has the S configuration. The implications for the stereochemistry of action of the latter enzyme are discussed.
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PMID:Absolute configuration of the diastereomers of adenosine 5'-O-(1-thiotriphosphate): consequences for the stereochemistry of polymerization by DNA-dependent RNA polymerase from Escherichia coli. 36 98

In an RNA-synthesizing system in vitro, a low-molecular-weight RNA consisting of about 110 residues (RNA-I) was efficiently synthesized on DNA of colicin E 1 plasmid (ColE1) and its deletion derivatives. The promoter site for RNA-I was analysed by testing the RNA polymerase-binding ability and template activity of restriction fragments; it was mapped in the region between the replication initiation site and the colicin immunity gene of ColE1. The direction of transcription was determined by hybridization tests to the separated strands of the template. The DNA region directing RNA-I was sequenced, and RNA-I was assigned on the sequence based on the nearest-neighbour data of RNA. The sequences of its promoter and terminator regions were also deduced. Although the function of this small RNA species is unknown, a unique secondary structure could be constructed from its sequence and sensitivity to RNase.
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PMID:The structure of a transcriptional unit on colicin E1 plasmid. 38 Sep 93

Two ribonuclease H activities have been found in yeast RNA polymerase A. The nuclease activities comigrated with subunits A49 (Mr = 49,000) and A40 (Mr = 40,000), after electrophoresis in a sodium dodecyl sulfate polyacrylamide gel containing [32P](rG)n . (dC)n as substrate. Both activities were also found, among other nucleases, in a high salt chromatin extract. Several lines of evidence suggest that the chromatin RNase H of 49,000 daltons (RNase H49) is the same protein as subunit A49. They co-migrate on sodium dodecyl sulfate-gel electrophoresis, have the same chromatographic properties, and dissociate simultaneously from RNA polymerase A. Fractions containing RNase H49 stimulate RNA synthesis by RNA polymerase A* lacking A49 and A34.5 subunits. Finally, limited proteolysis of the protein band having RNase H49 activity yields the characteristic fingerprint of the A49 subunit. This subunit, therefore, exists in two states: bound to chromatin and associated with RNA polymerase A. On the other hand, it is not yet clear whether the RNase H activity of 40,000 daltons, associated with RNA polymerase A, is due to the A40 subunit or whether it represents a trace contamination by a very active nuclease tightly bound to the enzyme.
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PMID:Identification of two different RNase H activities associated with yeast RNA polymerase A. 38 60

A DNA . protein complex of about 150 S is isolated from purified spinach chloroplasts by Sepharose 4B gel filtration. A DNA-dependent RNA polymerase activity is found associated with the complex. This DNA protein complex is able to initiate RNA chains in vitro. The RNA synthesis is more dependent on CTP than other nucleoside triphosphates. 50% of the activity is still present with 0.6 M KCl. The temperature optimum occurs between 30 degrees C and 35 degrees C. Rifampicin and rifamycin SV have no inhibitory effect. TNA products have been characterized by gel filtration and by hybridization with chloroplast DNA (ctDNA). At the beginning of transcription DNA products are linked to the transcription complex and are later detached. The molecular weight of the product ranges between 0.07 X 10(6) and 2 X 10(6). A part of the product (3--4%) has a molecular weight higher than 2 X 10(6). No endogenous RNase activity was present during the molecular weight determinations experiments. Hybridization experiments show that at least 75% of the RNA products are hybridizable with ctDNA and that 40% of these products are composed of chloroplast ribosomal RNA, showing that rDNA is preferentially transcribed.
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PMID:Transcription activity of a DNA-protein complex isolated from spinach plastids. 46 44

The effects of fasting, and subsequent force-feeding of L-tryptophan on the activity of hepatic nuclear DNA-dependent RNA polymerases were studied in adult (5-6 weeks old), and old (5-6 months) male Wistar rats. Liver nuclei, nucleoli, and nucleoplasmic fraction were isolated from rats following a single tube-feeding of tryptophan or water, and were assayed in vitro for the activity of different RNA polymerases. Whereas in adult rats 24 h of fasting caused a significant reduction in the activity of RNA polymerase I and II, in old rats the activity of only polymerase II was decreased after 24 h of fasting. In fasted adult rats administration of tryptophan promptly restored the activities of both polymerases to the respective normal fed levels, while in old rats none of the polymerases were affected by tryptophan. In fasted adult rats the pattern of response for both forms of polymerases to a single tube-feeding of tryptophan, over a period of 5 h, was found to be biphasic. When ribonuclease activity of nuclei was suppressed by performing incubations at low temperatures (17-30 degrees C) the difference between the two groups for polymerase I was greatly reduced, and for polymerase II the difference was fully abolished. Pre-treatment of fasted adult rats with cycloheximide (1.5 mg/kg) was found to abolish the 30 min tryptophan-mediated stimulation of both polymerase I and II activities. In cycloheximide pretreated rats the activity of polymerase II, but not polymerase I returned to its original level 5 h after tryptophan force-feeding.
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PMID:Effects of fasting and tryptophan force-feeding on the activity of hepatic nuclear RNA polymerases in rats. 52 54

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


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