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)

BK virus DNA can be extracted from virions as a nucleoprotein complex containing about 20 nucleosomes. Transcription of this "minichromosome" with Escherichia coli RNA polymerase indicates that both initiation and elongation of RNA chains are reduced by the presence of nucleosomes. Hybridization analysis of RNA made on the complex shows preferential transcription of one region of BK virus genome. No increase in strand selection is observed with respect to transcription of purified superhelical BK virus DNA.
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PMID:Minichromosome from BK virus as a template for transcription in vitro. 2 51

An in vitro RNA-synthesizing system consisting of gently lysed E. coli cells on cellophane discs is described. The system has been optimalized with respect to total RNA synthesis. Under certain standard conditions DNA dependent RNA polymerase (EC 2.7.7.6) is responsible for the majority of the RNA synthesis. The extensive rifampicin sensitivity of the synthesis indicates that most of the transcripts are initiated in vitro. The RNA synthesizing system described here has been developed with the aim of studying phage transcription in vitro. We show here that lysates of a P4 infected P2 lysogen support initiation and propagation of transcription from the P2 prophage.
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PMID:In vitro transcription in E. coli crude lysates prepared on cellophane discs. 2 67

1. When RNA polymerase is in excess over DNA, the single-stranded breaks of DNA can be recognized as initiation sites for the ezyme. On the other hand stabel initiation complexes (resistant to inhibition by heparin) are the most abundant under these conditions. The formation of these complexes needs double-stranded DNA. It seems that RNA sequences rich in cytidine are preferentially synthesized; since rat liver DNA is A + T-rich, the transcription thus appears not to be random with respect to the base composition of DNA. 2. When the template is in excess over the polymerase, the single-stranded gaps of DNA are preferentially transcribed by rat liver RNA polymerase B and native DNA regions by Escherichia coli RNA polymerase. 3. With a large excess of DNA over the polymerase, the enzyme activity is markedly inhibited. This inhibition is proportional to the concentration of double-stranded DNA ends, but it also depends on the presence of a contaminant of DNA, removed when DNA is banded in a CsCl gradient. This contaminant could be polyphosphates. Low concentrations of spermine completely reverse this inhibition, by enhancing the rate of RNA chain elongation. 4. Double-stranded RNA is synthesized in great abundance when RNA polymerase is in excess over native DNA. Besides a majority of symmetrical sequences, stable 'hairpins' can be found. Whereas the synthesis of symmetrical sequences is more prevalent in polymerase excess, it seems that the proportion of stable 'hairpins' in RNA is independent of the polymerase/DNA ratio.
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PMID:Transcription of rat liver deoxyribonucleic acid in vitro at low ionic strength. 3 73

Spontaneous mutants of Staphylococcus aureus resistant to rifampin, rifamycin SV, streptovaricin, or streptolydigin were isolated and shown to be resistant due to chromosomal rather than plasmid mutations. Based on data concerning spontaneous mutation rates, genetic cotransduction rates, and in vitro sensitivity studies, four major antibiotic cross-resistance patterns were found. The genetic markers responsible for these cross-resistance patterns were shown to be separable by transduction. Nonpurified RNA polymerase activity in lysates of mutants showed the same sensitivity to these antibiotics as shown by the mutants on solid media. A model is proposed explaining possible structure-function relationships involved in the binding of these antibiotics to the RNA polymerase molecule and the mutations resulting in resistance to these antibiotics. This model includes generally overlapping but different-sized binding sites on the RNA polymerase protein coded for by similarly arranged mutable sites on the DNA.
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PMID:Genetic analysis of Staphylococcus aureus RNA polymerase mutants. 3 50

RNA polymerase was extracted from the Schmidt-Ruppin strain of Rous sarcoma virus (SR-RSV)-induced C3H/He mouse ascites sarcoma cells (SR-C3H). RNA polymerase was separated into RNA polymerases I and II by DEAE-Sephadex chromatography. RNA polymerase I was separated into Ia and Ib fractions by phospho-cellulose chromatography. In SR-C3H cells RNA polymerase Ib was the main component of RNA polymerase I. At 0.05--0.1 M ammonium sulphate RNA polymerase I transcribed native DNA most actively, and RNA polymerase II transcribed denatured DNA most actively. Partial digestion of DNA by DNAase I enhanced RNA synthesis by RNA polymerases I and II. At ionic strength over 0.2 M ammonium sulphate, the initiation reaction of RNA polymerases I and II was inhibited. The initiation complexes of RNA polymerases I and II with native DNA were more stable against high salt concentration than with denatured DNA.
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PMID:Characterization of RNA polymerases from Rous sarcoma virus-induced mouse ascites sarcoma cells. 3 35

For the elucidation of the age-dependent reduction of the avidin induction in the ovidict of quails, studies on the level of the post-transcriptional events were performed. In estrogen-treated young animals, the extractable activity of DNA dependent RNA polymerase II increases by 145% after progesterone treatment, while in old animals no increase is observed. In the presence of actinomycin D the incorporation ratio [3H] Ado/[3H] Urd into mRNA increases by about 80% in the case of mature animals; this value is drastically lower (15%) using old animals. The activities of the poly(A)-degrading enzymes in oviducts of mature animals are lower than those in old ones. After progesterone treatment the activities of these enzymes increase in oviducts from old animals, while in young quails no alteration is observed. The possible consequence of these findings on the chain length of the poly(A) segment of mRNA is discussed with regard to its translation capacity.
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PMID:[Age-dependent avidin induction. V. Changes on the level of post-transcriptional modification]. 3 58

The in vivo binding of N-hydroxy acetylaminofluorene (N-OH AAF) to rat liver DNA was studied in hetero- and euchromatin fractions prepared by sedimentation through sucrose gradients. The greater transcriptional capacity of the slowly sedimenting (euchromatin) fractions was confirmed by their enhanced incorporation of radioactive precursors into RNA in vivo and their increased template activity for in vitro RNA synthesis by purified RNA polymerase. N-OH AFF was bound in 4- to 5-fold greater amounts to euchromatin DNA than to heterochromatin 2 h after a single injection of the compound. However, the bound carcinogen appeared to be eliminated more rapidly from euchromatin than from heterochromatin by DNA repair processes.
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PMID:Binding of N-hydroxy acetylaminofluorene to eu- and heterochromatin fractions of rat liver in vivo. 4 28

The proportion of cells absorbing trypan blue (tb-+ character) can be used to measure the late c.p.e. of wild-type poliovirus (ts-+. tb-+), which was the same at restrictive (39-2 to 39-6 degrees C) or permissive (37 degrees C) temperatures. Of twenty ts mutants, seven showed normal c.p.e. at 37 degrees C but were defective in C.P.E. (TB) AT 39-5 degrees C; all seven tb mutants have previously been shown (Cooper et al. 1971) to give evidence of a primary defect in replicase 1 activity (to make the complementary or minus strand of virus RNA). The remainder (tb-+) have all previously been shown to give evidence of a primary defect either in replicase II activity (to make progeny plus strands) or in structural protein. Thus, the late c.p.e. is dependent on a product of the replicase I gene, of which the in vivo effector is probably double-stranded RNA. Late c.p.e. is not caused by prevention of host protein, RNA or DNA synthesis and is not necessarily correlated with lysosomal enzyme release. The tb mutants were also defective in inducing early changes in chromatin (chr) and in prevention of thymidine incorporation (pti), but the tb and pti/chr characters are probably independent expressions of replicase I activity. Virus growth does not depend on repression of DNA synthesis. Poliovirus represses the activities of host DNA-dependent RNA polymerase I and II to an equal extent. There is no evidence that repression of DNA or RNA synthesis results from direct interaction of virus protein with the DNA.
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PMID:Poliovirus temperature-sensitivie mutants defective in cytopathic effects are also defective in synthesis of double-stranded RNA. 4 94

Although many researchers have reported that RNA synthesis in the ovary is enhanced by gonadotropin treatment, there are only a few papers concerning the character of newly synthesized RNA after gonadotropin treatment. In this paper, the RNA synthesized in the ovary of immature rats after HCG treatment was qualitatively studied. Immature female Sprague-Dawley rats were administered with 0.3 mc per rat of 3H-uridine at a certain time interval after injection of HCG (10 iu/rat) and the ovaries were subsequently isolated after 15, 30 or 60 minutes. RNA was extracted from the homogenate of the ovaries according to the hot phenol method after Scherrer and Darnell. The 3H-RNA thus extracted was treated with electrophoretically purified DNase to break down and remove DNA that mingled with it. The RNA solution ultimately obtained was analysed on a 3-20% sucrose gradient. The different fractions thus separated were then subjected to measurement of radioactivity and optical density at 260 mmug. The RNA extracted from the ovary of immature untreated rat labeled with 3H-uridine for 15 minutes showed a flat pattern of radioactivity from the top to the bottom fractions with low radioactivity. Otherwise, when labeled for one hour, the RNA showed a pattern of radioactivity like those of optical density at 260 mumu with peaks of r-RNAs and t-RNA. When the ovary was pulse-labeled with 3H-uridine for 15 minutes starting 2 hours after injection of HCG, the RNA with a large S value was synthesized and the pattern of variation in radioactivity was that of rising near the bottom fraction and declining with access to the top fraction. The results obtained by labeling for 15 minutes starting 40 hours after PMS administration were similar to those obtained in immature untreated rats. The patterns of radioactivity in RNA obtained by the labeling for 15 minutes starting 2 hours after HCG and 42 hours after PMS were similar to those starting 2 hours after only HCG injection. The patterns of radioactivity became similar to those of optical density at 260 mmu, when the ovaries were labeled for 30 or 60 minutes. From these results, it was suggested that the newly synthesized RNA 2 hours after HCG was constructed from m-RMA with rapid turn over and precursors of r-RNAs and t-RNA. This RNA synthesis was blocked by pretreatment with actinomycin but not by cycloheximide. From these results, it was suggested that enhancement in RNA polymerase activity or change in template capacity of DNA which would have an effect on RNA synthesis was not based on newly synthesized protein.
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PMID:[Studies on the RNA synthesized in the ovary of immature rats after HCG administration (author's transl)]. 5 Sep 55

At concentrations of 7 times 10(-6) to 7 times 10(-5) M, derivatives consisting of the polycylic ring structures fluoranthene, fluorenone, fluorene, anthraquinone, xanthenone, and dibenzofuran with appropriate amine side chains inhibited by over 90% the purified RNA-directed DNA polymerase of avian myeloblastosis virus acting on poly(deoxyadenylate-deoxythymidylate) [poly(dA-dT)]. Of these, only the fluoranthene derivatives were strong inhibitors of the viral DNA polymerase directed by polyadenylate-oligodeoxythymidylate [poly(A)-(dT)12-18]. Low levels of fluoranthene derivatives (1 times 10(-5) M) also strongly inhibited polymerase with polyinosinate-oligodeoxycytidylate [poly(I)-(dC)12-18], activated calf thymus DNA, and viral 70S RNA as templates, but not with polycytidylate-oligodeoxyguanylate as template. A comparison of the activity of 11 fluoranthene derivatives with different side chains showed that the structure of the amine side chain influenced both the extent of antipolymerase activity with a given template and the relative inhibition with different synthetic DNA and RNA templates. The naturally occurring polyamines, spermine, spermidine, and putrescine, did not inhibit the activity of the viral DNA polymerase. Studies on the mechanism of action indicated that the synthetic derivatives inhibited polymerase activity by binding to the template and not to the enzyme: 1) inhibition by fluoranthene derivatives was overcome by the addition of excess template including poly(dA-dT), poly(A)-(dT)12-18, poly(I)-(dC)12-18, viral 70S RNA, and activated calf thymus DNA; 2) the degree of inhibition by fluoranthene derivatives was unaffected by the addition of the creased viral DNA polymerase; 3) with the same template, Escherichia coli DNA-directed RNA polymerase and the viral RNA-directed DNA polymerase were inhibited to about the same extent; and 4) the derivatives formed a complex with DNA, poly(I), and poly(A) that was stable to exclusion chromatography on Sephadex G-100. Several derivatives also had biologic activity, since they blocked the ability of the murine sarcoma virus to transform cells.
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PMID:Inhibition of purified DNA polymerase of RNA tumor viruses by fluoranthene derivatives and analogues of tilorone hydrochloride. 5 Oct 87


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