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)

We have previously shown that when H4 hepatoma cells are pretreated with insulin, plant lectins, phorbol esters, or insulin mediator, the steady state concentration of gene 33 mRNA is markedly increased. The increase in gene 33 mRNA concentration with insulin is due to an increase in the transcription rate of this gene. In the present report we demonstrate that nuclear extracts prepared from H4 hepatoma cells pretreated with insulin exhibit enhanced transcription of gene 33 RNA from a DNA template containing the cap site and 1500 bp upstream of the 33 gene. This is a stable effect of insulin on the nuclear RNA polymerase II system since it is observed in frozen and thawed nuclear extracts as well as fresh nuclear extracts.
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PMID:Selective transcription of an insulin-regulated gene in nuclear extracts of rat hepatoma cells. 328 2

Nuclear extract from Morris hepatoma 3924A was fractionated by DEAE-Sephadex chromatography. The fraction eluting with 300 mM (NH4)2SO4 (DE-C) was used for transcribing cloned mouse metallothionein-I (MT-I) gene in a run-off assay. This fraction contained the majority of RNA polymerase II as well as the transcription factor(s). Accuracy of MT-I DNA transcription was confirmed by S1 nuclease mapping. Low concentrations (1 microgram/ml) of alpha-amanitin inhibited the reaction, indicating that RNA polymerase II directed the transcription. Unfractionated nuclear extracts from the hepatoma or a rat mammary adenocarcinoma as well as whole cell extract obtained from the mammary tumor also transcribed MT-I gene. The extent of transcriptional activity was in the following order: hepatoma nuclear fraction DE-C greater than whole cell extract derived from rat mammary adenocarcinoma cells greater than nuclear extract derived from rat hepatoma or rat mammary adenocarcinoma cells. These studies have demonstrated that a fractionated nuclear extract obtained from a tissue supports efficient and accurate RNA polymerase II-mediated transcription of MT-I DNA.
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PMID:Accurate transcription of mouse metallothionein-I gene in a fractionated nuclear extract from a rat hepatoma. 355

U6 RNA is an abundant, capped, small nuclear RNA (snRNA) species associated with heterogeneous nuclear ribonucleoproteins in eukaryotic cells. U4 RNA and U6 RNA are hydrogen bonded in a 1:1 ratio in discrete small nuclear ribonucleoprotein particles that are required in pre-mRNA processing. Previous reports have established that the mRNAs and U1 to U5 U-snRNAs are synthesized by RNA polymerase II. Evidence is presented here for synthesis of U6 RNA by RNA polymerase III. The synthesis of U6 RNA in vitro, using Novikoff hepatoma or HeLa whole cell extracts, was not inhibited at low (1 microgram/ml) concentrations of alpha-amanitin, and only 35% inhibition occurred at 10 micrograms/ml concentration. The in vitro synthesized U6 RNA, like other RNA polymerase III transcripts, was associated with La antigen. The U6 RNA synthesized in vitro by the whole cell extracts was capped, but no other internal post-transcriptional modifications were found. Uridylic acid residues were also added post-transcriptionally to the 3'-end of U6 RNA in vitro. U6 RNA, though capped on its 5'-end, is transcribed by RNA polymerase III; this is the first report of a capped RNA molecule synthesized by RNA polymerase III.
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PMID:The capped U6 small nuclear RNA is transcribed by RNA polymerase III. 379 36

Nuclear extracts obtained from normal rat liver and from Morris hepatoma 3924A were fractionated by DEAE-Sephadex chromatography. The fraction eluted with 175 mM (NH4)2SO4 (DE-B), which contains greater than 90% of RNA polymerase I activity, supported accurate transcription of cloned rat rDNA. A similar fraction obtained from the cytosol had all of the factors required for rDNA transcription. However, its transcriptional activity was at most one-sixth that of the corresponding nuclear fraction, as determined by the amount of protein needed to produce a similar quantity of the transcript. Unfractionated nuclear or cytosol preparations did not yield an accurate transcript. Optimal KCl and magnesium concentrations for rDNA transcription were 60 mM and 5-7.5 mM, respectively. The extent of transcriptional activity was in the following order: hepatoma nuclear fraction DE-B greater than whole cell extract derived from rat mammary adenocarcinoma cells much greater than normal liver fraction DE-B. The hepatoma preparation produced at least 10 times the amount of transcript produced by the corresponding liver nuclear preparation. Transcriptional activity was proportional to the levels of RNA polymerase I and to the rate of rRNA synthesis in these tissues.
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PMID:Accurate initiation of rat ribosomal RNA gene transcription using a fractionated nuclear extract from normal liver and a hepatoma. 385 47

Hydroxycamptothecin (HCPT) is an antitumor alkaloid isolated from Camptotheca acuminata indigenous to China. It could reduce the activity of nuclear RNA polymerase II and I(III) of hepatoma cells. HCPT at 25-100 microM caused a remarkable inhibition on DNA polymerase alpha whilst only a slight inhibition on beta. The inhibitory action on alpha was restored by increasing amounts of enzyme or DNA template, but unchanged by varying amounts of substrate. It is suggested that HCPT may exert a stronger inhibition on DNA replication process.
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PMID:The effect of hydroxycamptothecin in the activity of RNA and DNA polymerases prepared from murine hepatoma cells. 402 12

Plagemann, Peter G. W. (Western Reserve University, Cleveland, Ohio), and H. Earle Swim. Replication of mengovirus. I. Effect on synthesis of macromolecules by host cell. J. Bacteriol. 91:2317-2326. 1966.-The replication of mengovirus was studied in two strains of Novikoff (rat) hepatoma cells propagated in vitro. The replicative cycle in both strains required 6.5 to 7 hr. Infection resulted in a marked depression of ribonucleic acid (RNA) and protein synthesis by strain N1S1-63. Inhibition of RNA synthesis was reflected by a decrease in the deoxyribonucleic acid (DNA)-dependent RNA polymerase activity of isolated nuclei. Mengovirus had no effect on either protein or RNA synthesis or on the DNA-dependent RNA polymerase activity of a second strain, N1S1-67. The time course of viral-induced synthesis of RNA by cells was studied in cells treated with actinomycin D. It was first detectable between 2.5 and 3 hr after infection and continued until 6.5 to 7 hr. The formation of mature virus was estimated biochemically by measuring the amount of RNA synthesized as a result of viral infection which was resistant to degradation by ribonuclease in the presence of deoxycholate. Approximately 70% of the deoxycholate-ribonuclease-resistant RNA was located in mature virus, and the remainder was double-stranded. The formation of mature virus began about 45 min after viral-directed (actinomycin-resistant) synthesis of RNA was detectable in the cell, and only about 18 to 20% of the total RNA synthesized was incorporated into virus. Release of virus from cells began about 1 hr after maturation was first detectable. Release of virus from cells was accompanied by a loss of a large proportion of their cytoplasmic RNA and protein.
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PMID:Replication of mengovirus. I. Effect on synthesis of macromolecules by host cell. 428 85

Plagemann, Peter G. W. (Western Reserve University, Cleveland, Ohio), and H. Earle Swim. Replication of mengovirus. II. General properties of the viral-induced ribonucleic acid polymerase. J. Bacteriol. 91:2327-2332. 1966.-Mengovirus induces the appearance of a ribonucleic acid (RNA) polymerase activity in Novikoff hepatoma cells which is readily distinguished from the deoxyribonucleic acid (DNA)-dependent RNA polymerase since it is not inhibited by actinomycin D or deoxyribonuclease, but is inhibited by ammonium sulfate, and is stable at -17 C. The incorporation of uridine into RNA by infected cells in the presence of actinomycin D does not reflect the viral polymerase activity as measured in cell-free preparations. The viral-induced RNA polymerase is produced in a biphasic fashion. Puromycin inhibits the production of viral polymerase, and in its presence the enzyme appears to be unstable between 4 and 6 hr. Puromycin also prevents the secondary rise in polymerase which begins at the end of replicative cycle. Under these conditions, however, the polymerase appears to be stable. The overall data indicated that some unspecified process is responsible for the apparent instability of viral-induced RNA polymerase between 4 and 6 hr and that it becomes inoperative toward the end of the replicative cycle.
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PMID:Replication of mengovirus. II. General properties of the viral-induced ribonucleic acid polymerase. 428 86

To investigate the possibility that the pattern of multiple DNA-dependent RNA polymerases of an animal cell exerts a controlling influence on its nature, the activities of these enzymes were compared in differentiated rat liver and in a rapidly growing minimal-deviation rat hepatoma cell line by using established techniques of enzyme extraction, separation and determination. Relative to the DNA content of the tissues, RNA polymerase activities of forms AI, AII and B were approx. ninefold, twofold and twofold higher respectively in the cell line than in the liver. Tests indicated that these results could not be explained by differences in extraction efficiency or by the presence of unbound inhibitors or stimulators of polymerase activity in the final enzyme preparations. New forms of the enzyme were not detected in either tissue. The significance of these findings with respect to the possible role of multiple RNA polymerases in the control of cellular activities is discussed.
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PMID:Comparison of the multiple deoxyribonucleic acid-dependent ribonucleic acid polymerase forms of whole rat liver and a minimal-deviation rat hepatoma cell line. 434 94

The production of mengovirus in Novikoff rat hepatoma cells is progressively reduced with an increase in incubation temperature of the cells from 34 to 40 C, in spite of the fact that about the same amounts of single-stranded and double-stranded viral ribonucleic acid (RNA) are synthesized at 34, 37, and 40 C; the rate of overall protein synthesis is as high at 40 C as at 37 C. At 40 C, progeny viral RNA accumulates in an undegraded form without being incorporated into virus particles. The results suggest that virus maturation is preferentially inhibited at supraoptimal temperatures. At 42 C, on the other hand, no viral RNA is produced and no viral RNA polymerase activity is detectable in cell lysates. Failure of infected cells to form viral RNA polymerase at 42 C is probably due to an impairment of protein synthesis since most of the polyribosomes are rapidly lost during incubation at 42 C and the rate of amino acid incorporation into protein is 70% lower at 42 C than at 37 C. When infected cells are shifted from 37 to 42 C during the period of active viral RNA synthesis, viral RNA polymerase activity is rapidly lost from the cells, and viral RNA synthesis ceases within 45 min. In contrast, the RNA polymerase is as active in vitro at 42 C as at 37 C, and the activity is relatively stable at 42 C.
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PMID:Effects of elevated temperatures on mengovirus ribonucleic acid synthesis and virus production in Novikoff rat hepatoma cells. 554 27

The poly (A)-mRNA fraction isolated by chloroform deproteinization of liver polysomes and poly(U)-Sepharose chromatography contains a low molecular weights (congruent to 1000) peptidic fraction. The peptides which we suggested to call deprimerones (1) were extracted with 80% ethanol at pH 9.5; after ethanol evaporation, they were purified on Sephadex G-25 column as a fraction of mol. wt. between 1600 and 600, yielding about 9 mg/mg mRNA. If deproteinization is performed with phenol-chloroform the yield is about 2 mg/mg mRNA. In Novikoff hepatoma the yield of the same preparation is only 2.7 mg/mg mRNA (about 70% decrease). The obtained deprimerones are active in inhibiting transcription of thymus DNA with E. coli RNA polymerase and [3H]-GTP by about 90% at a ratio peptide/DNA = 2. For comparison the deprimerones obtained previously (2) by extraction of deproteinized DNA inhibit transcription only by about 50% at the same peptide/DNA ratio. The results demonstrated a decrease of the poly (A)-mRNA deprimerone level during carcinogenesis and further support the previously demonstrated specific occurrence of deprimerones with poly(A)-mRNA. They remain in accordance with and provide further support for the deprimerone theory of carcinogenesis postulated earlier (1).
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PMID:Poly(A)-mRNA deprimerones in rat liver and Novikoff hepatoma cells. 610 57


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