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)

RNA polymerase II was purified from Morris hepatoma 3924A by a series of ion-exchange and affinity column chromatographic fractionations, followed by sucrose gradient centrifugation in the presence of 0.3 M KC1. Purified RNA polymerase II had a specific activity of greater than 400 nmol of UMP incorporated (30 min)-1 (mg of protein)-1 by using double-stranded DNA as template. The purified enzyme contained five polypeptides (Mr 214 000, 140 000, 33 000, 25 000, and 21 000) that were present in molar quantities and two additional polypeptides (Mr 19 000 and 18 000) that had a combined molar ratio of 1.0. The cyclic AMP independent nuclear protein kinase NII, also purified from hepatoma 3924A, was able to phosphorylate RNA polymerase II polypeptides of Mr 214 000, 140 000, and 21 000. Phosphorylation of the polymerase was accompanied by enhanced transcription of double-stranded DNA, heat-denatured DNA, and poly[d-(A-T)]. The elevation in RNA polymerase activity was dependent upon the presence of hydrolyzable ATP and resulted from an increased number of RNA molecules synthesized in vitro. The average length of RNA chains was not affected by the kinase. Under similar conditions, protein kinase NII also stimulated homologous RNA polymerase I. In contrast to the phosphorylation of polymerase II, modification of polymerase I resulted in an increase in the average size, but not number, of RNA chains synthesized. The specificity of the NII kinase-catalyzed reaction was demonstrated by the inability of another homologous protein kinase, NI, to phosphorylate or activate RNA polymerase II.
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PMID:Phosphorylation of deoxyribonucleic acid dependent RNA polymerase II by nuclear protein kinase NII: mechanism of enhanced ribonucleic acid synthesis. 711 96

In nuclei and nucleoli of the slime mold Physarum polycephalum, ornithine decarboxylase (OrnDCase) (Mr 70,000) is phosphorylated by a protein kinase reaction that is dependent on spermidine and spermine. Putrescine antagonizes the phosphorylation. Phosphorylation of OrnDCase inhibits its capacity to catalyze decarboxylation of ornithine. The protein kinase that catalyzes this phosphorylation has many properties similar to those of nuclear protein kinase II, or type G, which has been studied by other groups. The interaction of this protein kinase with OrnDCase resembles the behavior of the OrnDCase antizyme described by other investigators. Phosphorylated OrnDCase binds to purified, palindromic rDNA isolated from nucleoli. It also stimulates transcription of the ribosomal genes by RNA polymerase I in a chromatin form of rDNA. It does not stimulate transcription in a purified, homologous transcription system comprised of RNA polymerase I, rDNA, and phospho-OrnDCase. Thus, phospho-OrnDCase may have a function in promoting rRNA gene transcription but the detailed mechanism is yet unclear. The polyamine-dependent protein kinase and its natural substrate of 70,000 daltons have been demonstrated in other eukaryotic cells, including bovine spermatozoa and rat liver nuclei, and in Ehrlich ascites tumor cells, where the protein kinase is induced by interferon. This phosphorylation system appears to be widely distributed and conserved among eukaryotic species.
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PMID:Posttranslational control of ornithine decarboxylase by polyamine-dependent protein kinase. 714 Oct 3

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

A nuclear protein kinase, designated NII, was purified essentially to homogeneity from the Morris hepatoma 3924A. In the presence of excess Mg2+, phosphorylation of casein by the kinase was stimulated by spermine (1-5 mM) and was inhibited completely by 0.1 microgram/ml heparin. The apparent Km for casein was reduced in the presence of spermine. Spermine preferentially augmented phosphorylation of threonine residues. The kinase was also associated with highly purified RNA polymerase I and appears to correspond to two polypeptides (Mr 42,000 and 24,600) of the polymerase. RNA polymerase I polypeptides of Mr 120,000 (S2), Mr 65,000 (S3) and Mr 24,600 (S5) were phosphorylated by the endogenous kinase. Spermine enhanced phosphorylation of the RNA polymerase I subunits as much as 20-fold. Phosphorylation activated RNA polymerase I; the phosphorylated enzyme synthesized longer product with no apparent effect on the number of RNA chains initiated.
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PMID:Spermine-mediated phosphorylation of RNA polymerase I and its effect on transcription. 733 1

For 3 yr, 1-yr synchronized circannual rhythms were found for the chick oviduct weights, amounts of soluble protein, concentrations of the progesterone receptor in this organ, and capacity of this steroid-receptor complex in cytosol in bind in vitro to deoxyribonucleoprotein acceptor sites. By fitting the data with 1-yr cosine curves, statistically significant circannual rhythms were described for all of these rhythms, with high values occurring in the late summer and low ones in the late winter. Interestingly, no statistically significant rhythms were described for the binding of the progesterone-receptor complex to pure DNA. By analyzing both receptor and nuclear protein preparations isolated at different times of the year, changes in the receptor were found to underlie the rhythms in nuclear binding in vitro. Studies in vivo revealed similar rhythms for the nuclear translocation and binding of both progesterone and estrogen and for the progesterone-induced changes in RNA polymerase II activity. In each instance, marked reductions in nuclear binding and steroid-induced changes in the polymerase activity occurred in the late winter. Blood levels of the 3H-labeled steroids did not vary throughout the year, so differences in whole body metabolism and disposition of the steroids were ruled out as factors in the in vivo rhythms. These results support the validity of the cell-free binding assays and the hypothesis that certain protein-DNA complexes, and not pure DNA, represent the natural acceptor sites for the progesterone receptor. Furthermore, these rhythms emphasize the fact that steroid receptors are not constant entities but change in both amount and function. Although the exact cause of these rhythms in the progesterone receptor is not understood, a rhythm in estrogen action on the oviduct is strongly suggested. These rhythms in the steroid receptors may play a role in seasonal reproduction and molting in animals.
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PMID:Circannual rhythms in steroid receptor concentration and nuclear binding in the chick oviduct. 740 70

A nonhistone chromosomal protein (D-55) of Mr 55000 has been isolated in homogeneous form from calf thymus by using the standard salt-extraction procedures for the isolation of nonhistone chromosomal proteins followed by hydroxyapatite chromatography. D-55 is further characterized as coming from the group of nonhistone chromosomal proteins easily phosphorylated by an endogenous nuclear protein kinase. The kinase incorporates 1 mol of phosphate per mol of protein from [gamma-32P]ATP. The unphosphorylated form of D-55 binds to DNA, histones, and nucleosomes. Phosphorylation of D-55 does not significantly alter the binding of D-55 to DNA but greatly enhances its binding to histones and nucleosomes. Binding of D-55 to reconstituted nucleosomes enhances transcription of the nucleosome DNA by E. coli RNA polymerase by approximately 100-fold, to a level approximately 4 times that observed with naked calf thymus DNA as template. Phosphorylation of D-55 abolishes this enhancement. Binding of D-55 produces no apparent alteration in nucleosome structure as assayed by nuclease digestion patterns. In contrast, phospho-D55 alters nucleosome structure significantly.
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PMID:Reversible phosphorylation of a nucleosome binding protein that stimulates transcription of nucleosome deoxyribonucleic acid. 745 45

We demonstrate here that stilbene estrogen (diethylstilbestrol) is converted to nuclear protein binding metabolite(s) both in vitro and in vivo. In vitro reaction of DES with nuclei from hamster liver or kidney in the presence of cumene hydroperoxide or NADPH revealed binding of [3H]DES in nuclear proteins (histones; nonhistones precipitable by 2% TCA, NH2; nonhistones soluble in 2% TCA, NH30). The binding was significantly inhibited by cytochromes P450 inhibitors. In an in vitro system [3H]DES quinone, one of the metabolites of DES, was able to bind to pure nonhistone proteins RNA polymerase and DNA polymerase. The binding of [3H]DES quinone to nonhistones RNA polymerase and DNA polymerase was inhibited by low molecular weight thiols, i.e. glutathione and cysteine, or thiol modifiers, such as n-ethylmaleimide, dithionitrobenzoic acid and hydroxymercuric benzoate. DES and DES metabolites inhibited transcriptional activity. In vivo [3H]DES was able to bind to nuclear proteins of hamster liver, kidneys and testes. The level of in vivo [3H]DES binding to all three types of nuclear proteins (histones, NH2, NH30) in the kidney (target organ) was two or more fold higher than that observed in the liver or testis (nontarget organs). Four nuclear NH30 proteins (mol wts.: 56, 37, 33 and 28 kDa) were irreversibly bound to [3H]DES in vivo. The in vivo binding of [3H]DES to transcriptionally active chromatin NH30 proteins also was observed. The data reported here establish that DES was able to bind to liver or kidney nuclear proteins in vitro, which was catalyzed by nuclear enzymes when fortified with an appropriate cofactor. DES quinone may be one of the protein binding metabolites. DES and DES metabolites inhibited transcriptional activity. The level of in vivo binding of [3H] DES to nuclear proteins of kidney (target organ) was double in comparison with that observed in liver or testis (nontarget organs). In vivo modifications in the chromatin proteins may be a factor in the development of DES-induced renal carcinogenesis is not clear.
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PMID:In vivo binding of diethylstilbestrol to nuclear proteins of kidneys of Syrian hamsters. 773 58

We have identified a temperature-sensitive mutant of Saccharomyces cerevisiae (npl3) that accumulates polyadenylated RNA in the nucleus at 37 degrees C, as judged by in situ hybridization. The strong nuclear signal is not simply due to increased cytoplasmic turnover of mRNA, as reincubation at 37 degrees C with an RNA polymerase inhibitor shows no diminution in the in situ signal. Over several hours at 37 degrees C, the average poly(A) tail length increases and a characteristic ultrastructural alteration of the nucleoplasm occurs. Cloning and sequencing indicate that the corresponding gene is NPL3/NOP3, which codes for a nucleolar/nuclear protein implicated in protein import into the nucleus (Bossie et al. (1992). Mol. Biol. Cell 3, 875-893) and in rRNA maturation (Russell and Tollervey (1992). J. Cell Biol. 119, 737-747). NPL3 includes bipartite RNA recognition motifs (RRM) and a Gly-Arg repeat domain, as in several nucleolar proteins. A point mutation adjacent to one of the RRM has been identified in the ts copy of the gene. Although this protein is not concentrated in nuclear pores, NPL3 is implicated in both import and export from the nucleus. Judging from the site of the npl3 mutation and since the block in RNA export can be detected prior to an obvious nuclear import defect in npl3, the defect in RNA export may be primary. Since other mutants that interrupt RNA export do not block protein import, the NPL3 protein itself appears to be implicated in protein import.
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PMID:A yeast protein that bidirectionally affects nucleocytoplasmic transport. 773 4

We have identified a set of genes that affect mRNA transport (mtr) from the nucleus to the cytoplasm of Saccharomyces cerevisiae. One of these genes, MTR2, has been cloned and shown to encode a novel 21-kDa nuclear protein that is essential for vegetative growth. MTR2 shows limited homology to a protein implicated in plasmid DNA transfer in Escherichia coli. PolyA+RNA accumulates within the nucleus of mtr2-1 in two to three foci at 37 degrees C. mRNA, tRNA, and rRNA synthesis continue as do pre-mRNA splicing, tRNA processing, and rRNA export at 37 degrees C. Under these conditions the polyA tail length increases, and protein synthesis is progressively inhibited. Nucleolar antigens also redistribute to two to three nuclear foci at 37 degrees C, and this redistribution depends on ongoing transcription by RNA polymerase II. Surprisingly, these foci coincide with the sites of polyA+RNA accumulation. Comparable colocalization and dependance on RNA polymerase II transcription is seen for the mtr1-1 mutant. The disorganization of the nucleolus thus depends on mRNA accumulation in these mutants. We discuss the possible functions of MTR2 and the yeast nucleolus in mRNA export.
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PMID:Nuclear mRNA accumulation causes nucleolar fragmentation in yeast mtr2 mutant. 786 87

Ku protein is a relatively abundant DNA-binding nuclear protein complex composed of two polypeptide subunits, p70 and p80. Ku has been recently identified as the regulatory component of the DNA-dependent protein kinase that phosphorylates RNA polymerase II. To further characterize in vivo regulation of Ku protein, we studied the expression of the transcripts coding for the Ku p70 and p80 subunits in different human cell lines and normal tissues by Northern blot hybridization, using specific cDNA probes. The expression level of both genes was approximately 10-fold higher in established cell lines than in normal tissues. However, mRNA expression levels in permanent cell lines correlated more strongly with their proliferative state than with their level of malignant transformation. In purified T lymphocytes induced to proliferate by the combined action of monoclonal antibodies directed against the CD2 and CD28 adhesion molecules, Ku p70 and p80 mRNA steady-state levels increased as soon as 6 h after activation and lasted at least 72 h. The human genes coding for the Ku p70 and p80 subunits were localized by cytogenetic mapping, using fluorescence in situ hybridization, to 22q13 and 2q33-->q35, respectively.
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PMID:Chromosomal location and expression of the genes coding for Ku p70 and p80 in human cell lines and normal tissues. 825 94


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