Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previous publications from this laboratory have demonstrated that agents such as methotrexate (MTX), 5-fluorodeoxyuridine (FUdR), trimethoprim, and D-glucosamine (D-GlcN), which are known to inhibit thymidylate synthesis, can augment human NK activity in vitro. Furthermore, this augmentation was inhibited by exogenous thymidine (TdR) at concentrations of 10(-6) to 10(-7) M. In this report, underlying mechanisms of action of FUdR, D-GlcN, and IFN are compared. Each of these agents increased the lytic activity of effector cells bound to targets but did not increase the percentage of conjugates formed. The augmentation could be induced in a population highly enriched for NK cells (Leu-1 lb positive in phenotype). FUdR and D-GlcN could not induce any augmentation in a Leu-1 lb-negative subpopulation whereas IFN could induce significant lytic activity. alpha-Amanitin, an inhibitor of RNA polymerase II, blocked the activation of NK activity by all three reagents; hence gene expression was required. Comparison of [35S]methionine-labeled proteins by two-dimensional gel electrophoresis revealed that six new proteins were induced in IFN-treated cells. Three of these were similar in pI and molecular weight to the newly synthesized proteins in the D-GlcN-treated cells. One protein was synthesized in increased amounts in the FuDR-treated cells and it was not common to either of the other treatments. Evidence to date is consistent with the hypothesis that separate mechanisms underlie the activation of NK cells by IFN and thymidylate synthesis inhibitors, although the existence of a final common pathway for all NK response modulators cannot be excluded at the present time.
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PMID:Studies on the mechanism of activation of human natural killer function by interferon and inhibitors of thymidylate synthesis. 244 44

The purpose of this study was to examine effects of aphidicolin and alpha-amanitin on visualization of acridine orange (AO) binding to DNA in rat astrocytoma C6 cells and to discuss briefly the significance of AO chromatin interaction products. Aphidicolin inhibited DNA synthesis but percentage of AO positive cells was approximately 60% of that of the untreated control cells. alpha-Amanitin caused a slight inhibition of RNA synthesis and 3H-uridine incorporation in the treated cells was about 64% of that of the untreated cells, whereas a distinct decrease of the number of AO positive cell nuclei was observed. The results suggest that activity of RNA polymerase II and mRNA synthesis is mainly concerned in visualization of AO chromatin interaction products.
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PMID:Effects of aphidicolin and alpha-amanitin on visualization of acridine orange binding to DNA in rat astrocytoma C6 cells. 258 4

The cytotoxicity of 5-fluorouridine (FUrd) results from actions directed at the synthesis of both DNA and RNA. The role of mRNA as a target for FUrd was investigated by selectively decreasing the incorporation of FUrd into RNA polymerase II transcripts of K-562 erythroleukemia cells, which was accomplished by the addition of alpha-amanitin to cultures of K-562 cells permeabilized with lysolecithin. In these cells alpha-amanitin at concentrations of 1-5 micrograms/ml inhibited the incorporation of [3H]-uridine into polyadenylated RNA by up to 45% and decreased the steady-state levels of two specific mRNAs but had no effect on poly A- RNA synthesis. alpha-Amanitin decreased the incorporation of FUrd into poly A+ RNA by up to 60%. The decrease in FUrd incorporation produced by alpha-amanitin was accompanied by an antagonism of the growth inhibitory effects of the fluorinated pyrimidine nucleoside by the mycotoxin, as measured by both growth in suspension culture and colony formation in 0.12% agar. Antagonism between these agents increased as the concentration of alpha-amanitin was elevated; furthermore, it was sequence-dependent, occurring only when alpha-amanitin preceded FUrd. These findings provide evidence that the actions of FUrd directed against mRNA are antagonized when FUrd incorporation into mRNA transcripts is decreased and that the effects of FUrd on mRNA produce cytotoxic consequences.
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PMID:RNA polymerase II transcripts as targets for 5-fluorouridine cytotoxicity: antagonism of 5-fluorouridine actions by alpha-amanitin. 273 15

Deletions in the promoter region of the 37S pre-rRNA operon in yeast were constructed and analysed in vivo using an artificial ribosomal minigene present on an extrachromosomal yeast vector. Sequences required for correct transcription initiation were found to be located between positions -192 and +15 relative to the start; a 5'-deletion down to position -133 reduces the transcription yield of the minigene at least five-fold. To allow detection of transcription of the minigene in isolated nuclei of yeast transformed with a minigene-bearing plasmid we attempted to increase the minigene copy number. The transcription yield in vivo appeared not to be proportional to the copy number but was found to be greatly enhanced when two or three minigenes are present in tandem. alpha-Amanitin sensitivity of transcription of these minigenes in isolated nuclei proved that RNA polymerase I is responsible for their transcription.
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PMID:Deletion mapping of the yeast Pol I promoter. 387 Sep 77

Synthesis of Rous sarcoma virus RNA was examined in vitro with a new assay for radioactive virus-specific RNA. Nuclei from infected and uninfected cells were incubated with ribonucleoside [alpha-(32)P]triphosphates, Mn(++), Mg(++) and (NH(4))(2)SO(4). Incorporation into total and viral RNA proceeded with similar kinetics for up to 25 min at 37 degrees . About 0.5% of the RNA synthesized by the infected system was scored as virus-specific, compared to 0.03% of the RNA from the uninfected system and 0.005% of the RNA synthesized by monkey kidney cell nuclei. Preincubation with DNase or actinomycin D completely suppressed total and virus-specific RNA synthesis. alpha-Amanitin, a specific inhibitor of eukaryotic RNA polymerase II, completely inhibited virus-specific RNA synthesis, while reducing total RNA synthesis by only 50%. We conclude that tumor virus-specific RNA is synthesized on a DNA template, most probably by the host's RNA polymerase II.
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PMID:In vitro synthesis of Rous sarcoma virus-specific RNA is catalyzed by a DNA-dependent RNA polymerase. 436 1

alpha-Amanitin acts in vitro and in vivo as a selective inhibitor of nucleoplasmic RNA polymerases. Treatment of mice with low doses of alpha-amanitin causes the following changes in the synthesis, maturation and nucleocytoplasmic transfer of liver RNA species. 1. The synthesis of the nuclear precursor of mRNA is strongly inhibited and all electrophoretic components are randomly affected. The labelling of cytoplasmic mRNA is blocked. These effects may be correlated with the rapid and lasting inhibition of nucleoplasmic RNA polymerase. 2. The synthesis and maturation of the nuclear precursor of rRNA is inhibited within 30min. (a) The initial effect is a strong (about 80%) inhibition of the early steps of 45S precursor rRNA maturation. (b) The synthesis of 45S precursor rRNA is also inhibited and the effect increases from about 30% at 30min to more than 70% at 150min. (c) The labelling of nuclear and cytoplasmic 28S and 18S rRNA is almost completely blocked. The labelling of nuclear 5S rRNA is inhibited by about 50%, but that of cytoplasmic 5S rRNA is blocked. (d) The action of alpha-amanitin on the synthesis of precursor rRNA cannot be correlated with the slight gradual decrease of nucleolar RNA polymerase activity (only 10-20% inhibition at 150min). (e) The inhibition of precursor rRNA maturation and synthesis precedes the ultrastructural lesions of the nucleolus detected by standard electron microscopy. 3. The synthesis of nuclear 4.6S precursor of tRNA is not affected by alpha-amanitin. However, the labelling of nuclear and cytoplasmic tRNA is decreased by about 50%, which indicates an inhibition of precursor tRNA maturation. The results of this study suggest that the synthesis and maturation of the precursor of rRNA and the maturation of the precursor of tRNA are under the control of nucleoplasmic gene products. The regulator molecules may be either RNA or proteins with exceedingly fast turnover.
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PMID:The action of alpha-amanitin in vivo on the synthesis and maturation of mouse liver ribonucleic acids. 447 81

Two deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerases (I, II) have been solubilized from isolated Saccharomyces cerevisiae nuclei. The enzymes can be separated by chromatography on O-diethylaminoethyl Sephadex. Both enzymes are active with high-molecular-weight nuclear yeast DNA, although RNA polymerase I has a higher affinity for polydeoxy-adenylic-thymidylic acid and RNA polymerase II for denatured DNA. RNA polymerase I is active only with manganese. alpha-Amanitin inhibits only the activity of RNA polymerase II.
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PMID:Nuclear deoxyribonucleic acid-dependent ribonucleic acid polymerases from Saccharomyces cerevisiae. 457 10

Three distinct species of ribonucleic acid (RNA) polymerase were resolved from Allomyces arbuscula by diethylaminoethyl-cellulose chromatography and characterized as to ionic strength and divalent cation preference. alpha-Amanitin specifically inhibited enzyme II; neither rifampin nor cycloheximide had any effect on the three enzymes. RNA polymerase was isolated from three stages of the diploid life cycle: the hyphal growth stage, mycelia in the process of forming sporangia, and the mitospores. The same three enzyme species could be resolved from each stage. Thus, there is no evidence from this work that RNA polymerase plays a major role in the control of development.
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PMID:Ribonucleic acid polymerase in Allomyces arbuscula. 472 72

alpha-Amanitin, a toxic substance from the mushroom Amanita phalloides, is a potent inhibitor of DNA-dependent RNA polymerase II (the nucleoplasmic form) from sea urchin, rat liver, and calf thymus. This compound exerts no effect on the activity of polymerase I (nucleolar form) or polymerase III (also nucleoplasmic). The inhibition is due to a specific interaction with polymerase II or with a complex of DNA and polymerase II.
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PMID:Specific inhibition of nuclear RNA polymerase II by alpha-amanitin. 491 58

1. alpha-Amanitin inhibits in vitro the activity of RNA polymerase II of rat brain nuclei. 2. The toxin does not pass the blood-brain barrier, but when injected intracerebrally is highly toxic for rats, and causes inhibition of RNA polymerase II of isolated brain nuclei. 3. Intracerebral injection of alpha-amanitin 6h before training to a passive avoidance task is followed by impaired performance of rats on retesting after 7 days, without affecting performance on retesting immediately after training.
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PMID:Effect of alpha-amanitin on ribonucleic acid polymerase II of rat brain nuclei and on retention of avoidance conditioning. 514 25


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