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)

Male rats were fed a diet containing 0.03% (w/w) 2-acetylaminofluorene (AAF) and their hepatic DNA was isolated and transcribed with E. coli RNA polymerase. Ingestion of the carcinogen-containing diet for 4 days substantially reduced the template capacity of the isolated DNA. This reduction in template capacity was due to an apparent decreased RNA chain size (up to 50%), with no significant changes in initiation or re-initiation of RNA synthesis. This premature termination of RNA synthesis was accompanied, in some instances, by a reduced rate of RNA chain elongation. When the rats were returned to a basal diet for 7 days following 4 days of AAF ingestion, template capacity and RNA chain size returned to control values. Fractionation of hepatic chromatin on a glycerol gradient revealed that inhibition of DNA template capacity occurs on portions exhibiting characteristics of expressed, as well as those with characteristics of repressed, segments of the genome. In contrast, the DNA isolated from a small, highly condensed chromatin fraction (15% of total chromatin-DNA) showed no significant reduction in total template capacity. Analysis of the fidelity of RNA synthesis on this DNA template was performed by determining the rate of addition of individual nucleotide triphosphates to a growing RNA chain. Large reductions in the rates of adenosine and uridine polymerization were observed while no changes in guanosine or cytidine polymerization were found. This suggests the presence of functionally significant carcinogen-induced modifications of adenine. The inhibition in the rate of adenosine and uridine polymerization was reversed when the animals were placed on a basal diet after AAF ingestion.
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PMID:Non-random nature of 2-acetylaminofluorene-induced alterations of DNA template capacity. 38 7

Minicells segregated from Escherichia coli chi925 carrying a drug-resistance plasmid were separated from nucleated cells by differential centrifugation and purified by rate-zonal centrifugation in sucrose gradients. Minicells purified in this way were capable of donating the plasmid to nucleated cells. They also incorporated thymidine, uridine and methionine into macromolecules. Methods are described for purification of plasmid-containing minicells on a scale large enough to allow isolation of DNA, DNA polymerase and RNA polymerase in sufficient quantities for studies of enzymes involved in replication and transcription of plasmid DNA.
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PMID:Isolation by differential and zonal centrifugation of minicells segregated by Escherichia coli. 38 90

The analysis of the transcriptional mechanism of the ribosomal RNA genes in Bacillus subtilis was undertaken by a study of the rRNA chain elongation in the presence of rifampicin. The residual RNA synthesis after the addition of rifampicin and [3H] uridine to exponentially growing cells has shown that 56% of the radioactivity incorporated into total RNA belongs to the unstable fraction and 44% to the fraction containing mature rRNA and tRNA. Such study allowed an estimation of the half-life of messenger RNAs as being approximately 2 min. The analysis of the transcription pattern of the ribosomal RNA genes, as measured by the amount of radioactivity found in the ribosomal subunits, was complicated by a contamination of the 30 S subunits by 50 S subunits. A contamination of approximately 15% was estimated by polyacrylamide gel electrophoresis and competitive hybridization. The ratios of incorporated radioactivity at zero time when drug and label were concomitantly added ranged between 5.4-6.0, after correction for this contamination. The decay of the 23 S rRNA followed a straight line which became parabolic in its final portion. These results, and theoretical considerations on the lag of rifampicin action and on the variance of the specific activity of the nucleotide pool at the very early times of the experimental observation, favor the interpretation that the 16 and 23 S rRNA genes in B. subtilis belong to the same transcriptional unit, being cotranscribed, in that order, by the same molecule of RNA polymerase. The transcriptional times of the 16 and 23 S rRNA genes were estimated as being 30 and 60 s, respectively.
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PMID:Ribosomal RNA genes in Bacillus subtilis. Evidence for a cotranscription mechanism. 40 54

Activities of DNA polymerases and RNA polymerases were studied by autoradiographic methods in growing and differentiating root cortex cells of Zea mays - a species in which endomitosis occurs - and Tulipa kaufmanniana - in which this process does not occur. In Tulipa kaufmanniana, the highest activity of DNA polymerase appears in the nuclei of meristematic zone during the S phase of the cell cycle. In Zea mays, endomitotic replication of DNA occurs in all growth and differentiation zones and the activity of DNA polymerase in the nuclei is similar to that in the meristematic zone. In both species, nuclear RNA synthesis, measured with 3H uridine incorporation, is highest in the meristematic zone and declines steadily with development. Activity of nuclear RNA polymerase is present in all developmental zones in both species and is similar to that in the meristematic zone. 3H uridine incorporation into nucleoli decreases markedly in both species, whereas the activity of nucleolar RNA polymerase remains at a high level in all root segments in Zea mays and decreases slightly in Tulipa kaufmanniana. It is argued that the differences between the incorporation of 3H uridine and that or 3H UMP may be caused by a reduction of the pool of endogenous ribonucleoside triphosphates. Marked activities of DNA polymerase and RNA polymerase in cytoplasm are possibly related to the growth and division of plastids and mitochondria.
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PMID:Activities of DNA polymerases and RNA polymerases detected in situ in growing and differentiating cells of root cortex. 42 7

The investigations of root meristems and hypocotyls of Lupinus albus L. starved, and then fed with 2% sucrose were carried out and several variations in nuclear and nucleolar dimensions, their ultrastructure, template activity of DNA, activities of RNA polymerases and transcriptional activity, were found. As a result of starvation, the surface area of nuclei and nucleoli decreases several times; after 24 hours, in the presence of sucrose, it grows again, but the control state is not achieved. Moreover, in a starved material the area of condensed chromatin in nucleus is increased by 1/3; after feeding, its partial recovery to the initial state is observed. The intensity of binding of 3H AMD in a fed material is increased by 1/3 as compared with the starved one. Transcriptional activity, estimated on the basis of 3H uridine incorporation is decreased in a starved material, especially in the meristematic tissue; feeding intensificates the transcriptional activity whereas the activity of endogenous RNA polymerase, investigated in hypocotyl, is drastically lowered in a starved material. Sucrose feeding does not restore the control state, though the per cent of nuclei and nucleoli revealing the activity of RNA polymerase is much higher in a fed material than in a starved one.
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PMID:Effect of starvation on the genetic activity of nucleus and nucleolar organizer. 43 79

Analogously as in the 32-cell stage [20], in the 4-, and 8-cell generations of antheridial filaments of Chara vulgaris, the activity of DNA dependent RNA polymerase detected in situ as well as the 3H uridine incorporation increase in the middle S phase and in the middle G2 phase, while they decrease considerably at the end of S phase and in late G2 phase. The diphasic changes occur both in the nucleolar and extranucleolar (nucleoplasmic) activity of RNA polymerase as well as in the 3H uridine incorporation. However, the maximum nucleolar activity, in both S and G2 phases, precedes the peak of nucleoplasmic activity. During the increased nucleolar activity RNA polymerase (as calculated per nucleus) shows a higher level as compared with nucleoplasmic RNA polymerase, whereas the intensity of 3H uridine incorporation into nucleous and nucleoplasm is similar. It may be supposed that the incubation environment containing Mg2+ used in vitro is more stimulating for the nucleolar RNA polymerase than for the nucleoplasmic RNA polymerase. The mean transcriptional activity of the nucleus and the activity of RNA polymerase in the 8-cell generation is about 20% lower than in the 4-cell generation, in proportion to the decrease in cell sizes.
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PMID:Changes in the activity of RNA polymerase detected in situ and the intensity of 3H uridine incorporation into the nucleolus and the nucleus of interphase cells in antheridial filaments of Chara vulgaris L. 48 62

Cladosporin, a fungal isocoumarin derivative, strongly inhibits the uptake and thereby the incorporation of uracil and leucine into cells of Bacillus brevis and the incorporation of uridine but not leucine into cells of the ascitic form of Ehrlich carcinoma (ECA) of mice. Normal uptake was not restored by removal of the antibiotic. In cells of Escherichia coli A 19-15 (met-) the inhibition of methionine uptake is associated with the cessation of growth. In a methionine-prototrophic revertant from this organism, the uptake of methionine is still inhibited; growth, however, is hardly affected by cladosporin. In vitro no effect on the DNA-dependent RNA polymerase from E. coli and on the RNA polymerase II from wheat germ could be detected. The poly(U)-directed poly(Phe) synthesis was also not inhibited by cladosporin. It is concluded that cladosporin inhibits uptake processes which, for the case of essential nutrients, leads to loss of viability.
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PMID:Metabolic products of microorganisms. 184. On the mode of action of cladosporin. 51 84

The effect of halothane on precursor incorporation into nucleic acids was studied in Tetrahymena pyriformis, a ciliate protozoan. At concentrations that blocked cell division (1.2 and 2.4 per cent), halothane inhibited incorporation of 14C-thymidine and 14C-uridine into DNA and RNA, respectively, in intact cells. However, in nuclei isolated from T. pyriformis, the anesthetic did not inhibit DNA and RNA synthesis when these processes were assayed using the nucleoside triphosphates (3H-thymidine triphosphate and 3H-uridine triphosphate) as precursors. It is concluded that halothane does not directly inhibit nucleic acid synthesis (i.e., the nucleic acid polymerase reactions), and that the inhibition of precursor incorporation observed in intact cells is due to an effect at a locus other than the DNA and RNA polymerase reactions.
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PMID:Halothane does not inhibit synthesis of nucleic acids in Tetrahymena pyriformis. 51 77

Investigations were conducted to test the effects of alpha-amanitin on RNA synthesis in preimplantation mouse embryos. Exposure of embryos in culture to 1-100 microgram/ml alpha-amanitin produced a dose- and time-dependence suppression of total RNA synthesis as measured by incorporation of [3H]uridine. Synthesis of polyadenylated RNA in blastocyst-stage embryos was abolished by alpha-amanitin-treatment at concentrations and exposure times that suppressed total RNA synthesis by less than 15%. DNA-dependent RNA polymerase activity was measured in lysates of embryos at several stages of preimplantation development. alpha-Amanitin suppressed total polymerase activity assayed under ionic conditions favorable to the detection of RNA polymerase II. Electrophoretic analyses revealed that preincubation of blastocysts in 100 microgram/ml alpha-amanitin reduced labelling of cytoplasmic 28S and 18S RNA by inhibition of both synthesis and maturation of nucleolar 45SrRNA-precursor. This action of alpha-amanitin on nucleolar RNA synthesis cannot be correlated with the minimal suppression of nucleolar RNA polymerase activity and suggests that the synthesis and processing of rRNA may be under control of nucleoplasmic gene products.
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PMID:Effects of alpha-amanitin on RNA synthesis by mouse embryos in culture. 64 76

A thermosensitive conditional yeast mutant (ts-187) which suppresses protein synthesis at the nonpermissive temperature (36 degrees C) also suppresses RNA synthesis. The effect of temperature on the mutant is similar to the addition of cycloheximide--it inhibits the incorporation of labeled precursors into RNA in both whole cells and isolated nuclei. The effect of temperature is selective for the RNA polymerases bound to the nuclear template but not for the total RNA polymerases. Thus, the specific activities and total amounts of RNA polymerase species extracted and assayed with exogenous DNA template are similar in the ts-187 cultured at 23 degrees C and at 36 degrees C. On the contrary, the nuclear polymerases, i.e., RNA synthesis in isolated nuclei, are dramatically inhibited in cells cultured at 36 degrees C. When amino acid starved ts-187 cells are transferred to 36 degrees C, release from the inhibtion of RNA synthesis is observed. As with the addition of cycloheximide, this relaxation is observed in cells but not in isolated nuclei. The parental strain, A364A, which responds by stimulating instead of inhibiting protein synthesis when the temperature is increased to 36 degrees C, also exhibits an inhibition in the incorporation of labeled precursor into RNA as well as reducing RNA synthesis in isolated nuclei. However, these are transitory inhibitions and afterward there is reinitiation of both processes. Reinitiation of RNA synthesis in isolated nuclei is similar to the relaxed phenomenon and it is called "nuclear relaxation". This relaxation can only be obtained if protein synthesis is not inhibited; however, cellular relaxation occurs in the absence of protein synthesis. The repression of the nuclear RNA polymerase activities which starvation and inhibition of protein synthesis produce appears to be due to a restriction in the nuclear DNA template. This notion is supported by the fact that a net diminution of these nuclear enzyme activities is observed in spheroplasts cultured under starving conditions. Studies of the four main ribonucleotide pools indicate that stringency and inhibition of protein synthesis (ts-187 cultured at 36 degrees C) produce an increase in UTP and CTP pools. This is consistent with the concept that stringency and inhibition of protein synthesis affect the rate of utilization rather than the synthesis of these ribonucleotide residues. In the A364A and ts-187 yeast strains, the conversion of uracil but not of uridine into the UTP and CTP is inhibited when there is inhibition of the nuclear RNA polymerases. This indicates that the uracil phosphoribosyltransferase but not the uridine-cytidine kinase is allosterically inhibited by UTP and CTP in yeast. The feedback inhibition in the metabolic pathway of the base explains why relaxation cannot be detected when uracil instead of uridine is used as the labeled RNA precursor.
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PMID:Control of ribonucleic acid synthesis in eukaryotes. 2. The effect of protein synthesis on the activities of nuclear and total DNA-dependent RNA polymerase in yeast. 77 13


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