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)

The putative structural gene encoding the vaccinia virus type I DNA topoisomerase (EC 5.99.1.2) was expressed in Escherichia coli under the control of a bacteriophage T7 promoter. Provision of T7 RNA polymerase resulted in the accumulation to high level of a Mr = 33,000 type I topoisomerase with the properties of the vaccinia enzyme. A simple purification scheme yielded approximately 8 mg of recombinant vaccinia topoisomerase from 400 ml of bacteria. DNA unwinding by the enzyme was stimulated by magnesium, manganese, calcium, cobalt, and spermidine, but inhibited by copper and zinc. Like eukaryotic cellular type I topoisomerases, but unlike the prokaryotic counterpart, the recombinant topoisomerase relaxed positively and negatively supercoiled DNA. The viral topoisomerase I was, however, resistant to the effects of camptothecin, a drug that specifically inhibits cellular type I topoisomerases.
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PMID:Characterization of vaccinia virus DNA topoisomerase I expressed in Escherichia coli. 284 43

The influence of cortisol on intestinal DNA-dependent RNA polymerase activity was studied in purified nuclei of vitamin D-deficient or 1,25-dihydroxyvitamin D3-treated chicks. Six- to 7-week-old vitamin D-deficient cockerels were given 5 mg of cortisol or vehicle intraperitoneally 24 and 48 hours before sacrifice. Three hours before sacrifice, 200 ng of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) was administered intracardially. Cortisol did not alter the uptake or metabolism of 1,25(OH)2D3 in the intestinal mucosa. After a 200 ng dose of 1,25(OH)2D3 the in situ intestinal ligated loop technique revealed a 39% increase in calcium absorption compared to control birds (P less than 0.001). The administration of cortisol (5 mg) to chickens given 1,25(OH)2D3, however, resulted in a significant decrease in intestinal calcium transport in vivo (P less than 0.0025). When intestinal nuclei were prepared from birds treated in a manner identical with that described above, 1,25(OH)2D3-treated and 1,25(OH)2D3 plus cortisol-treated chicks had intestinal RNA polymerase II transcriptional activities that were significantly greater than those of vitamin D-deficient controls (P less than or equal to 0.02, P less than or equal to 0.005). There was no difference between RNA polymerase II and I + III activities of the 1,25(OH)2D3-treated birds and that of the cortisol plus 1,25(OH)2D3-treated birds. Vitamin D-deficient chicks treated with cortisol alone showed RNA polymerase I + III activity that was significantly higher (P less than or equal to 0.01) than that of birds treated with vehicle alone.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Effect of cortisol on [3H] 1,25-dihydroxyvitamin D3 uptake and 1,25-dihydroxyvitamin D3-induced DNA-dependent RNA polymerase activity in chick intestinal cells. 310 75

DNA-dependent RNA polymerase was purified from Pseudomonas aeruginosa. The subunit structure was typical of other eubacterial RNA polymerases in having beta' (157,000), beta (148,000), sigma (87,000), and alpha 2 (45,000) subunits as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme was dependent on Mg2+, displaying optimal activity at 10 mM MgCl2. Ca2+ and Zn2+ could not replace MgCl2 in the assay system, while Mn2+, produced partial activity. KCl at concentrations greater than 10 mM inhibited enzyme activity. Optimal enzyme activity was observed at pH 8.5-9.0. The RNA polymerase was stable in 50% (w/v) glycerol at 4 degrees C for more than 3 months. Enzyme activity was inhibited in vitro by heparin, streptolydigin, streptovaracin, actinomycin D, and rifampicin.
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PMID:DNA-dependent RNA polymerase from Pseudomonas aeruginosa. 312 44

We report on the properties of a partially purified tRNA intron endonuclease from the archaebacterium Halobacterium volcanii. This enzyme is capable of precise excision of the 104-nucleotide intron from halo-bacterial pre-tRNA(Trp) substrates generated in vitro by T7 RNA polymerase transcription. The reaction requires divalent cations (Mg2+ or Ca2+) or spermidine, is inhibited by monovalent cations, and produces 5'-hydroxyl and 2',3'-cyclic phosphate termini. Unlike the universal substrate recognition properties characteristic of the eukaryotic tRNA intron endonucleases, this enzyme is specific for halophilic tRNA(Trp) substrates. The partially purified enzyme is not capable of removing the intron from a yeast pre-tRNA(Phe) substrate. Analysis of the enzyme's ability to cleave tRNA(Trp) substrates lacking exon sequences demonstrated that the mature tRNA-like structure is not required in the substrate. A substrate retaining the intact intron and only the anticodon stem and loop exon regions was efficiently cleaved. Deletions within the intron indicated that the intron was not a primary site for recognition by the endonuclease; however, its presence affects the efficiency of the cleavage reaction. The possible relationship of this enzyme to other RNA endonucleases is discussed.
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PMID:A tRNA(Trp) intron endonuclease from Halobacterium volcanii. Unique substrate recognition properties. 319 21

Purified RNA polymerase II from chicken leukemia cells was found to be an effective substrate for protein kinase C but not cAMP-dependent protein kinase. Protein kinase C catalyzed the incorporation of 1-2 mol of phosphate per mol of polymerase II and the reaction was totally calcium and lipid dependent. Electrophoresis studies revealed a time-dependent increase of phosphate incorporation into RNA polymerase II subunits of 220 KDa, 180 KDa and 150 KDa, with a preferential phosphorylation of the 180 KDa polypeptide. The phosphorylated enzyme has a preference for using single-stranded DNA as the template for transcription, including transcription of the single-stranded myb oncogene sequence. Phosphoamino acid analysis indicated that both serine and threonine residues were phosphorylated at equal amounts. Phosphorylation by protein kinase C increased the affinity of substrate-polymerase binding and the initial rate of RNA synthesis, suggesting a mechanism by which gene expression can be activated by protein kinase C.
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PMID:Protein kinase C phosphorylates leukemia RNA polymerase II. 347 67

Two high-affinity oestrogen receptors have been identified in the chick oviduct with equilibrium dissociation constants (Kd) of 0.1 and 1 nM, differing in their binding kinetics, role in ovalbumin synthesis and independent regulation in vivo. The higher-affinity receptor (X) increases RNA polymerase II activity directly, whereas the low-affinity receptor (Y) seems to be necessary to confer specificity to transcription of oestrogen-dependent genes. Acute administration of progesterone to oestrogen-stimulated chicks results in preferential destruction of the nuclear Y receptor accompanied by interruption of ovalbumin gene transcription. Here we demonstrate that receptor Y exists in a non-oestradiol binding form (Ynb) which can be activated to the binding form in vitro by treatment with either ATP or ADP. Furthermore, dialysis of oviduct cytosol, which has no effect on the high-affinity receptor X, converts receptor Y to Ynb; receptor Y can then be recovered by treatment with ATP in the presence of Mg2+ and independently of Ca2+. This is the first report of the controlled interconversion between a non-steroid binding form of oestrogen receptor and active receptor in a tissue that contains two independently regulated oestrogen receptor types.
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PMID:Reversible activation of non-steroid binding oestrogen receptor. 399 Aug 3

To determine whether 1 alpha, 25-dihydroxyvitamin D3-dependent increases in intestinal calcium uptake require de novo protein and RNA synthesis, the effects of several inhibitors of these processes have been re-examined in vitro using cultured embryonic chick duodenum. To minimize the contributions of antibiotic toxicity to the interpretation of results, care was taken to examine inhibitor effects at early times after the onset of the 1 alpha, 25-dihydroxyvitamin D3 response. Cycloheximide at a concentration of 5 microM blocked hormone-dependent calcium uptake at all times examined (6 to 24 h). Actinomycin D was similarly effective at 6 to 12 h. The effects of cycloheximide were totally reversible while actinomycin D inhibition was only partially reversible. These compounds inhibited protein or RNA synthesis by 68.4 +/- 1.4 and 51.4 +/- 1.1%, respectively. Anisomycin, another inhibitor of polypeptide chain elongation and alpha-amanitin, an inhibitor of RNA polymerase I, also blocked 1 alpha, 25-dihydroxyvitamin D3-dependent calcium uptake after 12 h in culture. These results further strengthen the hypothesis that 1 alpha, 25-dihydroxyvitamin D3 stimulates intestinal calcium transport via a nuclear mechanism involving new gene expression.
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PMID:The effect of inhibitors of protein and RNA synthesis on 1 alpha,25-dihydroxyvitamin D3-dependent calcium uptake in cultured embryonic chick duodenum. 616 75

Novel RNA polymerase activities (termed type II reaction) can be found in toluene-treated Escherichia coli with Ca2+, Fe2+, or endogenously bound cations, probably Mg2+. These activities are distinguishable from the well characterized DNA-dependent RNA polymerase (type I reaction) by: (i) their divalent cation requirements, i.e., the classical enzyme is activated by exogenously added Mn2+, Mg2+, or CO2+ ions; (ii) their relative resistance to inhibition by actinomycin D, rifampicin, and streptolydigin; (iii) their selective synthesis of low molecular weight RNA; (iv) their sensitivity to inhibition by arabinonucleoside 5'-triphosphates or deoxyribonucleoside 5'-triphosphates; and (v) the strict requirement for ATP in Ca2+ and bound cation-activated reactions. The Ca2+-activated and endogenous RNA polymerase activities are inhibited by orthophosphate. The properties of the type II RNA polymerase(s) are compared with those of polynucleotide phosphorylase, and dnaG gene product, and the RNA polymerase described by Ohasa and Tsugita.
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PMID:Divalent cation-activated RNA synthesis in toluene-treated Escherichia coli. 617 Apr 2

The effects of 14 metal ions (chlorides) on the transcription of calf thymus DNA and phage T4 DNA with Escherichia coli RNA polymerase were tested. These assays were conducted under improved conditions of lower pH and in the absence of 2-mercaptoethanol to permit greater stability of the metal ions in solution. Among the divalent metal ions tested, the concentration-dependent order of inhibition of overall transcription is Pb2+ greater than Zn2+ greater than Cu2+ greater than Be2+ greater than Cd2+ greater than Ni2+ greater than Ca2+ greater than Co2+ greater than Mn2+ greater than Mg2+ greater than Sr2+ and is the same with either template. At pH 7.4 and in the absence of 2-mercaptoethanol, considerably lower concentrations of several of the divalent metal ions are needed for inhibition of overall transcription than at pH 8.1 and in the presence of 2-mercaptoethanol. Ca2+, Mg2+, Sr2+, Zn2+, Li+, Na+, and K+--considered to be non-mutagenic and non-carcinogenic--decrease chain initiation (measured with T4 DNA) at concentrations that inhibit overall transcription. Pb2+, Cd2+, Co2+, Be2+, and Mn2+--all mutagenic or carcinogenic--stimulate chain initiation (although at widely different rates) at concentrations that inhibit overall transcription. Cu2+ and Ni2+--both carcinogenic--stimulate initiation only at very low concentrations, followed by a progressive decrease in initiation at concentrations that inhibit overall transcription.
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PMID:Selective effects of metal ions on RNA synthesis rates. 617 51

The hepatic uptake of 45calcium (45Ca) was studied in rats after administration of D-galactosamine (3 mmoles per kg, i.v.). In contrast to measurements of the hepatic calcium content, 45Ca uptake served as a dynamic rather than a static indicator of calcium homeostasis during the transition from reversible to irreversible liver injury which occurs between 3 and 4 hr after injection of the hepatotoxin. 45Ca uptake during a 1 hr-labeling period increased from 25 to 100% above control between 3 and 4 hr and subsequently remained at this level. The rise in 45Ca uptake and in hepatic calcium content occurred 2 to 3 hr after the D-galactosamine-induced depletion of UTP, UDP-galactose, UDP-glucose and UDP-glucuronate. The level of UDP-glucuronate was the earliest to recover. The enhanced 45Ca uptake was associated with hepatic glycogen breakdown and with an increased SGPT activity in plasma. Inhibition of RNA polymerase II by alpha-amanitin (0.5 mg per kg, i.p.) and of dolichol-dependent protein glycosylation as well as ganglioside synthesis by tunicamycin (2 mg per kg, i.p.) were used to imitate two of the early actions of D-galactosamine and indicated that an interference with either process can lead to an enhanced uptake of 45Ca into the liver in vivo. Uridine, at a dose replenishing uracil nucleotide pools after their depletion by D-galactosamine, prevented or reversed the rise in 45Ca uptake. The antiinflammatory steroid dexamethasone, injected prior to or simultaneously with D-galactosamine also protected against the loss of calcium homeostasis and the development of liver injury.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:45Calcium uptake during the transition from reversible to irreversible liver injury induced by D-galactosamine in vivo. 620 90


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