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 synthesis of RNA during mouse liver regeneration was studied by two different methods at 24 and 48 h after partial hepatectomy. Total chromatin-bound RNA polymerase activity showed an increase of 32% at 24 h after partial hepatectomy. At 48 h a slight increase in total activity was also observed in regenerating liver, but the difference was not significant. The increase in total RNA polymerase activity was due to a rise in RNA polymerase I plus III activity. This enzyme activity was increased at both 24 and 48 h. The increase was 57% at 24 h and 51% at 48 h. When [methyl-14C]methionine was used for labelling of methyl groups in rRNA, there was an increased specific radioactivity of this class of RNA at both 24 h and 48 h. The increases were 263 and 103% at 24 and 48 h respectively. Thus both methods revealed an increased synthesis of rRNA during mouse liver regeneration. The results are discussed in relation to previous results from this laboratory [Yngner, Carlberg, Lewan & Engelbrecht (1979) Hoppe-Seyler's Z. Physiol. Chem. 360, 1069-1074; Yngner, Engelbrecht, Lewan & Annerfeldt (1979) Biochem. J. 178, 1-8; Yngner, Bengtsson, Carlberg, Engelbrecht & Wieslander (1980) Exp. Cell. Biol. 48, 393-403], which have shown that the incorporation of orotic acid or uridine into RNA is not increased in mouse liver regenerating after partial hepatectomy.
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PMID:RNA synthesis in regenerating mouse liver evaluated by incorporation of [methyl-14C]methionine and by determination of RNA polymerase activity. 620 53

A poliovirus-specific RNA-dependent RNA polymerase was isolated from a cytoplasmic extract of infected HeLa cells and was shown to copurify with a single virus-specific protein. The polymerase was isolated from cells labeled with [35S]-methionine and was fractionated from other soluble cytoplasmic proteins by ammonium sulfate precipitation, phosphocellulose chromatography, gel filtration on Sephacryl S-200, and chromatography on hydroxylapatite. The activity of the enzyme was measured by using either polyadenylic acid or poliovirion RNA as a template in the presence of an oligouridylic acid primer. A single virus-specific protein that had an apparent molecular weight of 63,000 (p63) was found to copurify with this activity. Host-coded proteins were present in reduced molar amounts relative to p63. Noncapsid viral protein 2 (NCVP2) and other viral proteins were clearly separated from p63 by gel filtration on Sephacryl S-200. Polymerase activity coeluted from the column precisely with p63. NCVP2 was totally inactive as an RNA polymerase and did not stimulate the polymerase activity of p63. The purified enzyme sedimented at about 4S on a glycerol gradient and thus appeared to be a monomer of p63. Two-dimensional gel electrophoresis of the polymerase protein indicated that it had an isoelectric point of about 7.5. Thus, the viral polypeptide, p63, as defined by the above physical parameters, is an RNA-dependent RNA polymerase that can copy poliovirion RNA when oligouridylic acid is used as a primer.
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PMID:Identification of poliovirus polypeptide P63 as a soluble RNA-dependent RNA polymerase. 625 35

We have studied transcriptional initiation in the mitochondria of the yeast Saccharomyces cerevisiae by analyzing mitochondrial transcripts from grande and petite yeast after labeling in vitro with vaccinia virus guanylyltransferase and [alpha-32P]GTP. This procedure labels triphosphate-terminated RNA which arises from transcriptional initiation. Exploiting the extremely low GC content (18%) of yeast mitochondrial DNA, we digested the in vitro capped transcripts with the G-specific ribonuclease T1; this resulted in 27 oligonucleotides varying in size from 2 to 51 nucleotides. RNA from 14 overlapping petites was analyzed and 20 transcripts were localized by deletion mapping. Nineteen oligonucleotides were sequences and 13 were identified and precisely localized by comparison with known DNA sequences. In all cases, transcription is initiated at a consensus nonanucleotide sequence which can be considered part of the yeast mitochondrial promoter. We identified initiation sites for the 21 S and 14 S rRNAs; the phenylalanine, f-methionine, and glutamic tRNAs; two sites for the OLI-1 gene; and three for the ori (rep) regions. Most promoters appear to give rise to very long multigene primary transcripts. Examples are multigene transcripts for the glutamic tRNA and COB genes and for the OLI-1, serine tRNA, and Var genes. Since the consensus nonanucleotide sequences at the ori regions are similar to those at other transcriptional initiation sites, it is likely that the same RNA polymerase primes DNA replication and gene transcription.
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PMID:Identification of multiple transcriptional initiation sites on the yeast mitochondrial genome by in vitro capping with guanylyltransferase. 631 17

A temperature-sensitive coordinate mutant tsLA83 of Prague (PR-B) strain of Rous sarcoma virus at the nonpermissive temperature (41 degrees) produces noninfectious virus particles (NI-LA83) which contained only 3% of the reverse-transcriptase activity present in infectious virions. Analyses of [35S]methionine-labeled NI-LA83 showed the presence of all of the viral proteins except reverse transcriptase. Pulse-chase analyses of the virus-specified proteins in cells infected with LA83 or PR-B showed that the gag and glycoprotein precursors, Pr76gag and gPr95env, respectively, were processed at both 35 and 41 degrees. The reverse-transcriptase precursor, Pr180gag-pol, however, was not processed in LA83-infected cells at 41 degrees. In contrast, cells infected with LA83 or PR-B at 35 degrees as well as with PR-B at 41 degrees showed normal cleavage of Pr180gag-pol. A shiftdown of LA83-infected cells at 41 degrees to the permissive temperature 35 degrees resulted in the normal processing of Pr180gag-pol and production of infectious virus containing reverse transcriptase. Electron microscopic analysis showed that at 41 degrees cells infected with LA83 showed a large number of budding structures but fewer released particles. A shiftdown from 41 to 35 degrees resulted in an increase of virus particles with a concomitant decrease in budding structures suggesting that the processing of reverse-transcriptase precursor is related to virion assembly.
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PMID:Impaired cleavage of the joint gag-pol polyprotein precursor and virion assembly in a temperature-sensitive mutant of Rous sarcoma virus. 633 Sep 81

Half-lives of Myxococcus xanthus mRNA were determined by inhibiting RNA polymerase with rifampin and then measuring the rate of [35S]methionine incorporation into protein. Vegetative cells resuspended in clone fruiting liquid culture showed an average mRNA half-life of approximately 3.5 min. Developmental cells (24 or 48 hr) exhibited biphasic decay curves with apparent mRNA half-lives of approximately 3.5 min and 20-30 min. The more-stable mRNA species accounted for about 30% of all mRNA present in 24-hr cells and as much as 40% of all mRNA of 48-hr cells. Analysis of the 35S-labeled proteins by NaDodSO4/polyacrylamide gel electrophoresis showed that only 5-10 major polypeptides are synthesized after 30 min of rifampin treatment. One of these is protein S, the spore surface coat protein, because immunoprecipitation of the 35S-labeled proteins with antisera specific for protein S showed continued synthesis of protein S in the presence of rifampin. The half-life for its mRNA was calculated to be 15-30 min. RNA from vegetative and developing cells was pulse labeled with 32PO4 followed by rifampin treatment. Analysis of the labeled RNA on 3% NaDodSO4/polyacrylamide gels showed 5-10 long-lived mRNA bands in developing cells. These results show that there are several abundant mRNA species synthesized developmentally that are exceptionally long lived. The fact that the majority of the mRNA species show the shorter half-life suggests that developing cells retain the normal mechanism for mRNA degradation.
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PMID:Evidence for long-lived mRNA during fruiting body formation in myxococcus xanthus. 640 82

A lymphosarcoma cell line designated P1798.S6M has been characterized with respect to glucocorticoid responsiveness in culture. Cells ceased to proliferate in the presence of 10(-7) M dexamethasone. Cell viability remained high and glucocorticoid-sensitive cells could be rescued from cultures treated with dexamethasone for 24 or 48 h. These data indicate that P1798.S6M undergoes reversible arrest in the presence of dexamethasone. The system was used to study the effects of mitotic arrest upon transcription of rDNA. Incorporation of [methyl-3H]methionine into rRNA was rapidly inhibited and pulse-chase experiments indicated that 28 S RNA was not synthesized after 24 h of exposure to dexamethasone. Hybridization studies indicated that the amount of pre-rRNA was reduced by 90 to 95% in cells treated for 24 h. Transcription studies were carried out in isolated nuclei. Twenty-four hours after addition of dexamethasone, template-bound RNA polymerase I activity decreased by 89 to 96%. Total RNA polymerase I activity did not decrease, whereas disengaged nuclear polymerase I activity increased dramatically. Filter hybridization studies indicated that labeling of nascent pre-rRNA chains in vitro was inhibited 93%. These data are interpreted as follows: Dexamethasone reversibly inhibits proliferation of P1798.S6M cells and transcription of rDNA. Total RNA polymerase I activity does not decrease, but the amount of template-bound enzyme is reduced with a concomitant increase in the amount of disengaged polymerase I. This indicates that initiation of transcription is inhibited in cells undergoing mitotic arrest in the presence of dexamethasone.
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PMID:Hormonal regulation of transcription of rDNA. Inhibition of transcription during glucocorticoid-mediated inhibition of proliferation of lymphosarcoma P1798 cells in culture. 668 17

A cloned initiator methionine tRNA gene from Xenopus laevis has been transcribed in cell-free extracts (S-100) prepared from cultured X. laevis kidney cells. RNA polymerase III produces two primary transcripts of this gene which initiate with a pppG and a pppA located seven and four nucleotides, respectively, in front of the mature tRNAMet1 5' end. Both terminate with a dT5 tract just beyond the nucleotides encoding the mature tRNA. The tRNA precursors are readily processed in vitro to mature length tRNA which contains six of the seven modified nucleotides found in the in vivo tRNAMet1. Many of these ribonucleotide modifications (m1G, m2G, m7G, D, and m1A) are introduced into the primary transcripts. The single exception is t6A which is found in the tRNAMet1 anticodon loop only after maturation of the 5' and 3' termini.
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PMID:Synthesis and maturation of Xenopus laevis methionine tRNA gene transcripts in homologous cell-free extracts. 680 33

E. coli ribosomal protein L12, because of its unique features, has been studied in more detail than perhaps any of the other ribosomal proteins. Unlike the other ribosomal proteins that are generally present in stoichiometric amounts, there are four copies of L12 per ribosome, some of which are acetylated on the N-terminal serine. The acetylated species, referred to as L7, has not been shown, as yet, to possess any different biological activity than L12. A specific enzyme that acetylates L12 to form L7, using acetyl-CoA as the acetyl donor, has been purified from E. coli extracts. L12 is also unique in that it does not contain cysteine, tryptophan, histidine, or tyrosine, is very acidic (pI: 4.85) and has a high content of ordered secondary structure (approximately 50%). The protein is normally found in solution as a dimer and also forms a tight complex with ribosomal protein L10. There are three methionine residues in L12, located in the N-terminal region of the protein, one or more of which are essential for biological activity. Oxidation of the methionines to methionine sulfoxide prevents dimer formation and inactivates the protein. The four copies of L12 are located in the crest region(s) of the 50S ribosomal subunit. There is good evidence that the soluble factors, such as IF-2, EF-Tu, EF-G and RF, interact with L12 on the ribosome during the process of protein synthesis. This interaction is essential for the proper functioning of each of the factors and for GTP hydrolysis associated with the individual partial reactions of protein synthesis. The L12 gene is located on an operon that contains the genes for L10 and beta beta' subunits of RNA polymerase at about 88 min on the bacterial chromosome. DNA-directed in vitro systems have been used to study the unique regulation of the expression of these genes. Autogenous regulation, translational control, and transcription attenuation are regulatory mechanisms that function to control the synthesis of these proteins.
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PMID:Chemistry and biology of E. coli ribosomal protein L12. 701 80

The genome-enzyme complex is isolated from the silkworm cytoplasmic polyhedrosis virus with DEAE-Sephadex column chromatography after ultraviolet irradiation. The genome-enzyme complex shows both RNA-polymerase and methyltransferase activities while using 3H-UTP and [3H-methyl]-S-adenosyle-L-methionine as substrates. Like the double-stranded RNA genome of CPV, the genome-enzyme complex could be separated into nine segments on polyacrylamide gel electrophoresis. It is demonstrated that the RNA polymerase and methyl-transferase are tightly bound to the double-stranded RNA genome and that the individual segments of the genome-enzyme complex all possess RNA-polymerase and methyltransferase activities. It appears that each segment of the double-stranded RNA genome is transcribed independently.
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PMID:Isolation of genome-enzyme complex from cytoplasmic polyhedrosis virus of silkworm Bombyx mori. 704 27

When 3-day-old etiolated soybean seedlings are treated with the synthetic auxin, 2,4-dichlorophenoxyacetic acid, cells of the mature hypocotyl swell and proliferate abnormally. By 48 h after auxin application ribonucleic acid (RNA) polymerase I and II levels increase by about 10-20- and 6-fold, respectively, on a fresh weight tissue basis and about 3-6- and 2-fold, respectively, on a tissue deoxyribonucleic acid (DNA) basis. [35S]Methionine incorporation into RNA polymerase subunits suggests that this increase in levels of RNA polymerases results from de novo synthesis of the enzymes. No alteration in subunit structure or patterns of incorporation of [35S]methionine into RNA polymerase subunits is detected following auxin treatment. No differences in the phosphorylation patterns of RNA polymerase subunits are detected after hormone treatment. These results indicate that although the levels of RNA polymerases I and II may regulate, in part, the rates of transcription during physiological or developmental transitions, alteration or modification of RNA polymerase subunit structure does not appear to be involved in transcriptional regulation in the auxin-induced soybean hypocotyl.
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PMID:Auxin-induced deoxyribonucleic acid dependent ribonucleic acid polymerase activities in mature soybean hypocotyl. 719 81


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