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)

Explant outgrowths from human fetal brain were infected with 104 plaque forming units of the E variant of the encephalomyocarditis virus. Ultrastructurally, the majority of the cultured cells were astrocytes containing a moderate amount of glial fibrils. The earliest alterations at 44 hrs after infection of the culture consisted of dilatation of the rough endoplasmic reticulum (ER) and moderate enlargement of the mitochondria with increased density of their matrix. Twenty hours thereafter, increased amounts of the rough ER and of free ribosomes were observed in the infected cells. This was followed by aggregates of larger dense particles which developed into a parallel lattice-like pattern within the cytoplasm, presumably presenting viral particles, without obvious cytonecrosis. The present observations of the continuous development of the crystalloid formation of the virus within the cytoplasmic matrix as well as the mode of formation of the free ribosomes adjacent to the ER support the previous hypothesis that, after the uptake of the virus into the cytoplasmic matrix, it associates with the ER, where production of viral RNA polymerase and of viral RNA is initiated.
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PMID:Ultrastructural alterations of tissue cultures from human fetal brain infected with the E variant of EMC virus. 17 Jul 75

The results of steroid hormone stimulation of aggregate RNA polymerase ?activity in kidney can be interpreted in terms of either template or enzyme alterations. In order to discover the effect of aldosterone on enzyme or DNA template, the RNA polymerases were purified from kidney nuclei of normal, adrenalectomized or adrenalectomized plus aldosterone treated rats and the activity was determined using different sources of DNA. It was found that the DNA from aldosterone treated rats was transcribed more efficiently than from other sources. Aldosterone does not seem to have a direct effect on the RNA polymerase. Fractionation of ([14-C]aldosterone injected) kidney chromatin revealed the presence of radioactivity in the non-histone acidic proteins and DNA, suggesting the possible binding of aldosterone or aldosterone-receptor complex to these chromatin fractions which may result in enhanced template activity. Turnover of RNA was also studied in various subcellular fractions: nuclei, mitochondria, rough endoplasmic reticulum, smooth endoplasmic reticulum, polysomes, ribosomes and sRNA, in normal, adrenalectomized, and adrenalectomized plus adrenocortical hormone treated rat kidney, by following the loss of radioactivity after a single injection of [14-C]-orotic acid. Daily administration of aldosterone or deoxycorticosterone reversed the effects of adrenalectomy. Daily administration of corticosterone was without effect.
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PMID:RNA polymerase stimulation: effect of aldosterone and other adrenocorticoids on RNA turnover in rat kidney. 112 Feb 93

The open reading frame potentially encoding a 78 amino acid, 9101 Da hydrophobic protein (HP) and, mapping at the 3' end of the porcine transmissible gastroenteritis coronavirus (TGEV) genome, was shown to be expressed during virus replication. The cloned HP gene was placed in a plasmid under control of the T7 RNA polymerase promoter and in vitro translation of transcripts generated in vitro yielded a 9.1-kDa protein that was immunoprecipitable with porcine hyperimmune anti-TGEV serum. Antiserum raised in rabbits against a 31 amino acid synthetic polypeptide that represented the central hydrophilic region of HP specifically immunoprecipitated HP from TGEV-infected cells. HP was further shown to become associated with microsomal membranes during synthesis in vitro and was found to be closely associated with the endoplasmic reticulum and cell surface membranes in infected cells. The intracellular location of HP suggests that it may play a role in the membrane association of replication complexes or in virion assembly.
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PMID:The 9-kDa hydrophobic protein encoded at the 3' end of the porcine transmissible gastroenteritis coronavirus genome is membrane-associated. 131 Jan 91

Ricin B chain (RTB) is an N-glycosylated galactose-specific lectin which folds into two globular domains. Each domain binds one galactoside. The x-ray crystallographic structure has shown that the two binding sites are structurally similar and contain key binding residues which hydrogen bond to the sugar, and a conserved tripeptide, Asp-Val-Arg. We have used oligonucleotide site-directed mutagenesis to change either the binding residues or the homologous tripeptide in one or other or in both of the sites. The 5' signal sequence and RTB coding region were excised from preproricin cDNA and fused in frame to generate preRTB cDNA. Transcripts synthesized in vitro from wild-type or mutant preRTB cloned into the Xenopus transcription vector pSP64T using SP6 RNA polymerase, were microinjected into Xenopus oocytes. The recombinant products were segregated into the oocyte rough endoplasmic reticulum and core-glycosylated, and the N-terminal signal peptide was removed. Mutating sugar binding sites individually did not abrogate the lectin activity of RTB. When both sites were changed simultaneously, RTB was produced which was soluble and stable but no longer able to bind galactose. Changing the Asn residues of the two RTB N-glycosylation sites to Gln showed that oligosaccharide side chains were essential for both the stability and biological activity of recombinant RTB.
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PMID:Mutational analysis of the galactose binding ability of recombinant ricin B chain. 171 62

The simian rotavirus SA11 genome segment 10 codes for a nonstructural glycoprotein, NS28, that has been hypothesized to be involved in budding of viral particles into the endoplasmic reticulum (ER) membrane. Previous studies had suggested that NS28 is an integral membrane protein of the ER, possibly a transmembrane protein. We have examined the topography of NS28 inserted in microsomal membranes following cell-free translation of genome segment 10 transcripts. These transcripts were obtained either by hybrid selection of mRNA synthesized by the endogenous viral RNA polymerase or by in vitro transcription of genome segment 10 cDNA using SP6 polymerase. Full-length and truncated gene 10 transcripts were translated in a cell-free system supplemented with dog pancreatic microsomes. The existence of a cytoplasmic domain of the translation product was demonstrated by protease protection experiments. An 18,000 (18K) mol wt glycosylated polypeptide was protected from digestion with proteinase K and trypsin, whereas chymotrypsin digestion yielded a 23K mol wt glycosylated polypeptide. Correlation of these biochemical data with the known sequence of NS28 suggests that a 10K mol wt hydrophilic, carboxy-terminal fragment (from amino acid number 86 to amino acid number 175) of this glycoprotein is exposed on the cytoplasmic side of the ER membrane. A model of how NS28 folds in the ER membrane is proposed.
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PMID:Topography of the simian rotavirus nonstructural glycoprotein (NS28) in the endoplasmic reticulum membrane. 283 61

We have cloned the gene encoding a novel small cytoplasmic RNA from the fission yeast Schizosaccharomyces pombe. Four lines of evidence support the idea that this RNA is a homolog of the 7SL RNA component of mammalian signal recognition particle (SRP), which targets presecretory proteins to the endoplasmic reticulum membrane. First, it shares limited but significant primary sequence homology with previously identified 7SL RNAs and can be folded into a similar secondary structure. Second, it possesses the 5' triphosphate characteristic of unprocessed RNA polymerase III transcripts, and moreover, it is the only fission yeast RNA in this size range with such a terminus. Third, its behavior in cell fractionation experiments suggests that it is part of a small ribonucleoprotein which forms salt-labile contacts with larger structures. Fourth, the particle containing S. pombe 7SL RNA resembles mammalian SRP in both size (11S) and affinity for DEAE-Sepharose. Disruption of the single-copy gene, designated slr1+, reveals that the RNA is indispensable for growth in fission yeast. This result is not surprising, since secretion is an essential cellular process.
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PMID:Identification of an essential Schizosaccharomyces pombe RNA homologous to the 7SL component of signal recognition particle. 283 48

This communication presents our recent studies on the biosynthesis of influenza virus hemagglutinin (HA) in a mammalian-cell-free system and its translocation across microsomal membranes. RNAs coding for wild-type (full-length) and mutant (truncated) forms of HA were generated by in vitro transcription by using bacteriophage T7 DNA-dependent RNA polymerase. These RNAs were translated in a rabbit reticulocyte system that was supplemented with dog pancreas membranes, either before translation was initiated or after it had been artificially terminated with the antibiotic cycloheximide. All forms of HA could be cotranslationally translocated. However, only truncated molecules (83% of full length) could translocate after protein synthesis had been terminated. Posttranslational translocation was dependent on the presence of a functional N-terminal signal sequence and occurred only in the presence of ribosomes. The molecular mechanism of protein targeting and translocation across the membrane of the endoplasmic reticulum is discussed based on the signal hypothesis.
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PMID:Uncoupling of translocation across microsomal membranes from biosynthesis of influenza virus hemagglutinin. 337 4

Cytoplasmic extracts of chicken embryo fibroblast cells infected with Semliki Forest virus were subjected to isopycnic centrifugation in discontinuous sucrose gradients. Seven distinct bands were usually formed. The four upper bands contained predominantly smooth membranes and the lowest band was enriched in rough endoplasmic reticulum. One fraction (fraction 5), banding at a density of 1.16 g/cm(3), was found to be heavily enriched in pulse-labeled ribonucleic acid (RNA), viral RNA polymerase, and viral RNA forms associated with RNA replication. Thus, fraction 5 evidently contained a membrane-associated viral replication complex of a type previously defined in picornavirus infections. Fraction 5 was also consistently enriched with unique membranous structures previously observed in intact cells as type 1 cytopathic vacuoles (CPV-1). When the CPV-1 in fraction 5 were isolated from cells briefly incubated with (3)H-uridine and (3)H-adenosine prior to cell disruption, a large proportion was found to be labeled by high-resolution autoradiography. Thus, ultrastructural, biochemical, and biological evidence were all consistent with the interpretation that the CPV-1 membranes represent a significant element of the viral replication complex.
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PMID:Membrane-associated replication complex in arbovirus infection. 434 56

1. Aflatoxin B(1), administered in vivo, inhibits the incorporation of [(14)C]orotic acid in vivo into rat liver nuclei, and also inhibits both Mg(2+)- and Mn(2+)-dependent RNA polymerase activities in nuclei assayed in vitro. 2. Aflatoxin B(1) inhibits the cortisol-induced increase in incorporation of [(14)C]leucine in vivo, but does not affect the control value of this activity. 3. Aflatoxin B(1) administered in vivo inhibits the increase in nuclear Mg(2+)-dependent RNA polymerase activity, assayed in vitro, which results from the treatment with cortisol. 4. Adrenalectomy causes a decrease in Mg(2+)-dependent RNA polymerase activity. The effect on this enzymic activity of adrenalectomy plus treatment with aflatoxin B(1) is no greater than that of treatment with aflatoxin B(1) alone. 5. These results suggest that the inhibition of cortisol-stimulated biochemical pathways by aflatoxin B(1) is due to an inhibition of cortisol-stimulated RNA synthesis. 6. The cytoplasmic action of aflatoxin is thought to be due to a competition for receptor sites on the endoplasmic reticulum between steroid hormones and aflatoxin B(1). No evidence was obtained for a similar competition for nuclear receptor sites between [(3)H]cortisol and aflatoxin B(1). 7. No differences were observed between the activities of RNA polymerase preparations solubilized from control or aflatoxin-inhibited nuclei. 8. No differences in ;melting' profiles were observed between DNA and chromatin preparations isolated from control nuclei or from aflatoxin-inhibited nuclei. 9. It is suggested that aflatoxin B(1) exerts its effect on RNA polymerase by decreasing the template capacity of the chromatin and that the aflatoxin ;target' area of the chromatin includes that region which is stimulated by cortisol. This process, however, does not involve inhibiting the movement of cortisol from the outside of the hepatic cell to the nuclear chromatin.
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PMID:The effect of aflatoxin B 1 on normal and cortisol-stimulated rat liver ribonucleic acid synthesis. 466 88

An endonuclease, which was originally identified for its RNA polymerase inhibitory activity, was isolated from rat liver endoplasmic reticulum. The enzyme yields on gel chromatography four active fractions of different molecular weights (Mr 5.3 X 10(4), 9 X 10(4), 1.55 X 10(5) and Sephacryl S-200 fraction at V0). Each fraction contains polypeptide chains which give a single band on sodium dodecylsulphate electrophoresis (Mr 5.4 X 10(4). This indicates that the enzyme is an oligomeric protein and each of its subunits exhibits the same or very similar molecular weights. Deoxyribonucleoside and ribonucleoside triphosphates can bind to the endoplasmic reticulum nuclease. Binding is enhanced in the presence of divalent cations particularly Mg2+. The enzyme exhibits mainly RNase activity but can also degrade denatured DNA and DNA . RNA hybrids which contain breaks in one of the two strands. Poly(A) and mainly poly(U) are most susceptible to its nucleolytic activity whereas poly(C) is completely resistant.
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PMID:Endoplasmic reticulum nuclease. Purification and specificity. 627 70


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