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)

Evidence is presented that isoproterenol treatment of rat C6 glioma cells, under conditions that increase glioma cell cAMP levels, causes the phosphorylative modification of several RNA polymerase II subunits. RNA polymerase II in control and isoproterenol-stimulated 32Pi-labeled confluent glioma cells was immunoprecipitated from ribonuclease-treated nuclear extracts with hen anti-calf RNA polymerase II antiserum conjugated to Sepharose. The immunoprecipitated RNA polymerase II was analyzed for 32P-labeled subunits by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels. Using this technique, we have shown that isoproterenol causes a time-dependent increase of phosphate incorporation into RNA polymerase II subunits of 214,000, 180,000, 140,000, 35,000, 28,000, and 16,500 daltons. Phosphate incorporation occurred exclusively on serine in all of the six subunits. About 0.5-2 mol of phosphate/mol of RNA polymerase II subunit were incorporated. Dibutyryl cAMP (10(-3)M) mimics the stimulatory action of isoproterenol and mediates increased phosphate incorporation into the six subunits. (RS)-propranolol (10(-4)M) prevents the isoproterenol-mediated phosphorylative changes. These data indicate that isoproterenol, via cAMP, mediates a transient structural modification of RNA polymerase II subunits in rat C6 glioma cells which may possibly lead to a modulation of RNA polymerase II function(s).
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PMID:Phosphorylation of rat C6 glioma cell DNA-dependent RNA polymerase II in vivo. Identification of phosphorylated subunits and modulation of phosphorylation by isoproterenol and N6,O2'-dibutyryl cyclic AMP. 609 70

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

Nuclear protein kinases include enzymes that transfer the gamma-phosphate of ATP to serine, threonine, lysine or histidine in proteins. Nuclear kinases with a preference for basic proteins are known as histone kinases; those preferring acidic protein substrates are casein kinases. Histone kinases include both cyclic AMP-independent protein kinases and cyclic AMP-dependent protein kinases. The best-characterized cyclic AMP-independent nuclear protein kinase is associated with cell proliferation and is activated (or transported to the nucleus) in G2 phase of the cell cycle. It phosphorylates specific serine and threonine residues in the non globular domains of histone H1 and appears to promote chromosome condensation. The cyclic AMP-dependent protein kinase has unknown nuclear function(s), although it may be translocated from cytoplasm to nucleus in response to specific hormonal stimuli which are also associated with changes in transcriptional activity. There is a massive peak of nuclear cyclic AMP-dependent protein kinase activity in G2 phase of the cell cycle. Nuclear casein kinases are apparently very heterogeneous. Two of these enzymes have been purified to homogeneity. They phosphorylate non-histone chromosomal proteins, including RNA polymerase and ornithine decarboxylase. Phosphorylated ornithine decarboxylase is inactive enzymatically but, in Physarum, it binds to the rDNA minichromosome and stimulates rRNA transcription. Kinases forming phosphoramidate bonds occur in a variety of rat tissues and form phosphohistide in histone H4 and phospholysine in histone H1.
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PMID:Nuclear protein kinases. 632 62

The rate of adaptation of Escherichia coli K-12 NF930 spoT1 cells with elevated intracellular level of ppGpp to various minimal media was studied. It has been found that the rate of adaptation of spoT cells, like that of parent and rel strains, depends mainly on the rate of derepression of the ilv operon. The maximal rate of the ilv operon derepression was observed when an optimal concentration of ppGpp was maintained in cells. Derepression of the ilv operon is sharply delayed when the level of ppGpp is elevated or reduced. Mutations altering the translation system do not change the rate of adaptation of spoT cells. Rifampicin resistance mutations which altered the structure of RNA polymerase change the rate of adaptation of spoT cells to minimal media, especially to those containing serine at high concentrations. The possible role of serine in the regulation of ppGpp degradation system is discussed.
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PMID:[Expression of the amino acid operons in Escherichia coli strains with an altered transcription and translation apparatus. IV. The effect of mutations disturbing the coupling of the transcription and translation processes on ilv-operon expression in cells carrying the mutation in the spoT gene]. 635 48

More than 40 protein species including RNA polymerase were found to be phosphorylated in Escherichia coli on analyses of 32P-labeled cell lysates by single and two-dimensional gel electrophoresis and autoradiography. The protein species and the level of phosphorylation varied depending on the cell growth phase. With [gamma-32P]ATP as a substrate, cell lysates phosphorylated endogenous proteins in vitro which were predominantly phosphorylated in vivo. Both serine and threonine were the major phosphate acceptors in whole cell lysates. Starting from a partially purified RNA polymerase preparation with the protein phosphorylation activity and using an E. coli protein with an apparent Mr = 90K (K represents X 1000) as the substrate, we purified a protein kinase with a native Mr approximately 120K to apparent homogeneity. The protein kinase is either a heterodimer of 61K and 66K polypeptides or a homodimer of one of these polypeptides. We also isolated a 100K protein with self-phosphorylation activity.
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PMID:Protein phosphorylation in Escherichia coli and purification of a protein kinase. 636 41

A number of proteins of the sulphur-dependent archaebacterium Sulfolobus acidocaldarius are phosphorylated in vivo. The extent of phosphorylation depends on the state of growth and is most intense in the late exponential phase. Some of the phosphorylated proteins are strongly associated with the bacterial membrane. Ribosomal proteins and DNA-dependent RNA polymerase are not phosphorylated. Studies in vitro show a high target selectivity. The activity is not increased by cyclic nucleotides. The reaction in vitro is optimal in the presence of Mg2+, Mn2+ or Ca2+. Both serine and threonine residues are modified. Acetate ions do not induce additional phosphorylation.
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PMID:Protein phosphorylation in the archaebacterium Sulfolobus acidocaldarius. 643 62

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

We have recently purified a cyclic nucleotide-independent, heparin-sensitive nuclear protein kinase (NII) from Morris hepatoma 3924A and demonstrated an apparent relationship of this kinase to the two subunits (Mr = 42,000 and 24,600) of RNA polymerase I. When homogeneous protein kinase NII was recombined with purified homologous RNA polymerase I containing limiting quantities of endogenous kinase, RNA synthesis was stimulated as much as 5-fold during a 90-min incubation. The enhanced RNA synthesis was due to an increase in the average RNA chain length; protein kinase did not alter the number of RNA molecules synthesized by the polymerase. Phosphorylation of RNA polymerase occurred at serine and threonine moieties. Unlike the NII kinase, purified homologous NI kinase did not phosphorylate RNA polymerase I and, as a result, did not alter transcription. These data indicate that 1) RNA polymerase I is activated by protein kinase NII, 2) endogenous protein kinase NII remaining with highly purified RNA polymerase I does not fully phosphorylate RNA polymerase I in vitro, and 3) protein kinase NII is capable of regulating RNA polymerase I activity by preventing premature termination of RNA chains.
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PMID:Activation of purified hepatoma RNA polymerase I by homologous protein kinase NII. 728 32

Rabbit hemorrhagic disease virus, a positive-stranded RNA virus of the family Caliciviridae, encodes a trypsin-like cysteine protease as part of a large polyprotein. Upon expression in Escherichia coli, the protease releases itself from larger precursors by proteolytic cleavages at its N and C termini. Both cleavage sites were determined by N-terminal sequence analysis of the cleavage products. Cleavage at the N terminus of the protease occurred with high efficiency at an EG dipeptide at positions 1108 and 1109. Cleavage at the C terminus of the protease occurred with low efficiency at an ET dipeptide at positions 1251 and 1252. To study the cleavage specificity of the protease, amino acid substitutions were introduced at the P2, P1, and P1' positions at the cleavage site at the N-terminal boundary of the protease. This analysis showed that the amino acid at the P1 position is the most important determinant for substrate recognition. Only glutamic acid, glutamine, and aspartic acid were tolerated at this position. At the P1' position, glycine, serine, and alanine were the preferred substrates of the protease, but a number of amino acids with larger side chains were also tolerated. Substitutions at the P2 position had only little effect on the cleavage efficiency. Cell-free expression of the C-terminal half of the ORF1 polyprotein showed that the protease catalyzes cleavage at the junction of the RNA polymerase and the capsid protein. An EG dipeptide at positions 1767 and 1768 was identified as the putative cleavage site. Our data show that rabbit hemorrhagic disease virus encodes a trypsin-like cysteine protease that is similar to 3C proteases with regard to function and specificity but is more similar to 2A proteases with regard to size.
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PMID:3C-like protease of rabbit hemorrhagic disease virus: identification of cleavage sites in the ORF1 polyprotein and analysis of cleavage specificity. 747 37

We have previously shown that the exchange of the discriminator base A73 of human tRNA(Leu) for G is alone sufficient to achieve complete loss of leucine acceptance and to create an efficient serine acceptor. The reverse identity switch, however, which was studied using T7 RNA polymerase transcripts of in vitro mutagenized tRNA genes, reveals a far more complex pattern of identity elements for tRNA(Leu). Introduction of the following tRNA(Leu)-specific structures is necessary to transform human tRNA(Ser) into an efficient leucine acceptor: the discriminator base A73, the base pairs C3:G70, A4:U69 and G5:C68 of the acceptor stem, C20a of the DHU loop and the long extra arm. In contrast to tRNA(Ser), human tRNA(Leu) identity requires both the sequence and the correct orientation of the long extra arm, whereas only its orientation is essential for serine identity.
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PMID:Identity elements of human tRNA(Leu): structural requirements for converting human tRNA(Ser) into a leucine acceptor in vitro. 747 89


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