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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)

Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase activity was assayed on nuclear preparations of chick embryo fibroblast cells at various times after infection with an influenza A virus (fowl plague virus) and was compared with the activity of uninfected cells. Polymerase activity was increased by about 60% by 2 hr after infection, and this increase coincided with an increase in RNA synthesis in infected cells, as determined by pulse-labeling with uridine. No difference could be detected between the polymerases of infected and uninfected cells as to their requirements for DNA primer, divalent cations, and nucleoside triphosphates, and they were equally sensitive to addition of actinomycin D to the reaction mixture. It is possible that host cell DNA-dependent RNA polymerase is involved in the replication of influenza virus RNA.
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PMID:Deoxyribonucleic acid-dependent ribonucleic acid polymerase activity in cells infected with influenza virus. 574 27

Influenza virus infection has adverse effects on the metabolism of two representative RNA polymerase II transcripts in chicken embryo fibroblasts, those coding for beta-actin and for avian leukosis virus (ALV) proteins. Proviral ALV DNA was integrated into host cell DNA by prior infection with ALV. Within 1 h after influenza virus infection, the rate of transcription of beta-actin and ALV sequences decreased 40 to 60%, as determined by labeling the cells for 5 min with [3H]uridine and by in vitro, runoff assays with isolated nuclei. The transcripts that continued to be synthesized did not appear in the cytoplasm as mature mRNAs, and the kinetics of labeling of these transcripts strongly suggest that they were degraded in the nucleus. By S1 endonuclease assay, it was confirmed that nuclear ALV transcripts disappeared very early after infection, already decreasing ca. 80% by 1 h postinfection. A plausible explanation for this nuclear degradation is that the viral cap-dependent endonuclease in the nucleus cleaves the 5' ends of new polymerase II transcripts, rendering the resulting decapped RNAs susceptible to hydrolysis by cellular nucleases. In contrast to the nuclear transcripts, cytoplasmic beta-actin and ALV mRNAs, which are synthesized before infection, were more stable and did not decrease in amount until after 3 h postinfection. Similar stability of cytoplasmic host cell mRNAs was observed in infected HeLa cells, in which the levels of actin mRNA and two HeLa cell mRNAs (pHe 7 and pHe 28) remained at undiminished levels for 3 h of infection and decreased only slightly by 4.5 h postinfection. The cytoplasmic actin and pHe 7 mRNAs isolated from infected HeLa cells were shown to be translated in reticulocyte extracts in vitro, indicating that host mRNAs were not inactivated by a virus-induced modification. Despite the continued presence of high levels of functional host cell mRNAs, host cell protein synthesis was effectively shut off by about 3 h postinfection in both chicken embryo fibroblasts and HeLa cells. These results are consistent with the establishment of an influenza virus-specific translational system that selectively translates viral and not host mRNAs.
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PMID:Metabolism and expression of RNA polymerase II transcripts in influenza virus-infected cells. 609 46

Influenza viral RNA transcription in the infected cell is inhibited by alpha-amanitin, a specific inhibitor of the host nuclear RNA polymerase II. Because viral RNA transcription in vitro catalysed by the virion-associated transcriptase is greatly enhanced by the addition of a primer dinucleotide, ApG or GpG, we have proposed that viral RNA transcription in vivo requires initiation by primer RNAs synthesized by RNA polymerase II. In addition, because we did not detect any capping and methylating enzymes in virions, we have proposed that the 5' terminal methylated cap found on in-vivo viral messenger RNA (mRNA) is derived from the putative primer RNAs. Our recent experiments have proved these two hypotheses. Purified globin mRNAs were shown to stimulate viral RNA transcription in vitro very effectively. The resulting transcripts directed the synthesis of all the non-glycosylated virus-specific proteins in cell-free systems. Other eukaryotic mRNAs were also active as primers. The presence of a 5' terminal methylated cap structure in the priming mRNA was required for its priming activity. Thus, with globin mRNA, removal of the cap eliminated essentially all of its priming activity, and much of this activity could be restored by enzymically recapping the globin mRNA. Using globin mRNA containing 32P only in its cap, we demonstrated that the 5' cap of the globin mRNA primer was physically transferred to the viral RNA transcripts during transcription. Gel electrophoretic analysis suggested that, in addition to the cap, about 10-15 other nucleotides were also transferred from the globin mRNA to the viral RNA transcripts. A mechanism for the priming of influenza viral RNA transcription by globin mRNA is proposed. Initial experiments strongly suggest that priming by capped host mRNAs also occurs during the synthesis of viral mRNA in vivo.
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PMID:RNA primers and the role of host nuclear RNA polymerase II in influenza viral RNA transcription. 610 53

Reverse transcriptase has been shown to transcribe virion DNA of influenza A virus without an exogeneous primer. At least six virion RNA segments are transcribed with the formation of complementary 4S DNA product. A possible primer function of hairpin structures at the 3'-end of virion RNA segments is discussed.
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PMID:[Reverse transcription of influenza virion RNA without exogenous primer]. 617 95

Foscarnet has previously been shown to inhibit influenza RNA polymerase activity. In this report the mode of inhibition of foscarnet has been investigated by enzyme-kinetic procedures and product analysis. Foscarnet shows noncompetitive inhibition with respect to ATP, CTP, and UTP, and a mixed inhibition with respect to GTP. In the presence of foscarnet the initiation of the mRNA synthesis can still occur, but the elongation is inhibited. The block of mRNA formation by foscarnet seems to occur after the synthesis of the 12-nucleotide-long conserved sequence found at the 5 prime end of the viral message.
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PMID:Mode of interference of trisodium phosphonoformate (INN: foscarnet sodium), with influenza virus mRNA synthesis. 623 85

We propose a mechanism for the priming of influenza viral RNA transcription by capped RNAs in which specific 5'-terminal fragments are cleaved from the capped RNAs by a virion-associated endonuclease. These fragments would serve as the actual primers for the initiation of transcription by the initial incorporation by the initial incorporation of a G residue at their 3' end. We show that virions and purified viral cores contain a unique endonuclease that cleaves RNAs containing a 5' methylated cap structure (m7GpppXm) preferentially at purine residues 10 to 14 nucleotides from the cap, generating fragments with 3'-terminal hydroxyl groups. RNAs containing the 5'-terminal structure GpppG could not be cleaved to produce these specific fragments. Consistent with our proposed mechanism, those capped fragments that function as primers could be linked to a G residue in transcriptase reactions containing alpha-32P-GTP as the only ribonucleoside triphosphate. The pattern of G and C incorporation onto these primer fragments suggests that this incorporation is directed by the second and third bases at the 3' end of the virion RNA template, which has the sequence 3' UCG. Primer fragments with a 3'-terminal A residue were used more efficiently than those with a 3'-terminal G residue, indicating a preference for generating an AGC sequence in the viral mRNA complementary to the 3' end of the virion RNA. Cleavage of the RNA primer and initiation of transcription are not necessarily coupled, because a 5' fragment isolated from one reaction could be used as a primer when added to a second reaction. Uncapped ribopolymer inhibitors of viral RNA transcription inhibited the cleavage of capped RNAs.
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PMID:A unique cap(m7GpppXm)-dependent influenza virion endonuclease cleaves capped RNAs to generate the primers that initiate viral RNA transcription. 626 60

A systematic and comparative study was performed on the polypeptide composition and the RNA polymerase activity associated with virions of various strains of influenza A virus, including four human and two avian viruses. Significant differences were found in the molecular weights of not only hemagglutinin (HA) but also both nucleoprotein (NP) and membrane protein (M), as determined by polyacrylamide gel electrophoresis under denaturing conditions. The results indicate that, among viruses sharing the same serotype determined by the surface proteins HA and NA (neuraminidase), considerable variations exist in the structure of viral proteins, including inner proteins. The relative contents of viral proteins also varied among these strains grown under similar conditions. The total content of three P proteins, the putative RNA polymerase subunits, was within the range between 1.1 and 2.2% of total viral proteins and roughly paralleled the virion-associated RNA polymerase activity. The virion-associated RNA polymerase of all the strains tested were stimulated by the same dinucleotide primers, ApG or GpG, indicating that the specificity of transcription initiation is conserved among wide varieties of influenza virus.
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PMID:RNA polymerase of influenza virus. I. Comparison of the virion-associated RNA polymerase activity of various strains of influenza virus. 627 72

Administration of a single-stranded polynucleotide copolymer containing 9% cytidine residues and 91% 4-thiouridine residues [poly(C,S4U10)], a known potent inhibitor of the virion transcriptase of influenza viruses, suppressed the amount of virus recoverable from the nasal washes of influenza virus-infected hamsters and ferrets. The incidence of sneezing and nasal discharge in infected ferrets was also reduced. In hamsters, poly(C,S4U10) was more effective than amantadine-HCl or Virazole. Polyinosinic acid in combination with poly-5-hydroxy cytidylic acid also had anti-influenza effects. Poly(C,S4U10) annealed to polyadenylic acid was not effective, nor was the double-stranded polymer (polyinosinic acid) . (polycytidylic acid) even when complexed with carboxymethylcellulose and polylysine. No toxic effects of poly(C,S4U10) were apparent in the treated hamsters and ferrets, and high doses (greater than or equal to 2.86 g/kg) administered intraperitoneally to mice produced no adverse effects.
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PMID:Antiviral effects of single-stranded polynucleotide inhibitors of the influenza virion-associated transcriptase against influenza virus infection of hamsters and ferrets. 628 Jun 8

Substituted methylene diphosphonates are effective inhibitors of the RNA polymerase of influenza A virus causing 50% inhibition of the polymerase activity when they are present in the concentration range 10-85 microM. The inhibitory power of the methylene diphosphonates appears to be related to their ability to chelate with metal ions.
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PMID:The inhibition of the RNA polymerase activity of influenza virus A by pyrophosphate analogues. 631 May 7

The influenza virus A/duck/Alberta/48/76 with the antigen formula H7N3 (16) and Hav1 Nav2 (WHO nomenclature from 1971) (15), respectively, as well as a nonpathogenic virus of the subtype Hav1 were purified to a high degree by ultracentrifugation in continuous sucrose gradients (15-40% w/w and 20-60% w/w, respectively). The activity of the RNA polymerase of this virus preparation was determined by incorporating 3H-UMP in acid insoluble material following preincubation of the virus with the nonionic detergens Nonidet P-40 for 15 min at 32 degrees C. The influence of different concentrations was investigated of dinucleotid, NaCl, MgCl2, Nonidet P-40 and different incubation temperatures. Optimal incorporation rates were found at following conditions: 0.2 mM dinucleotid ApG, 150 mM sodium chloride and 8 mM magnesium chloride by concentration of ions, 0.25-0.5% detergens Nonidet P-40 as well as a temperature of incubation of 32 degrees C. The data for optimal polymerase activity for the avian influenza virus A/duck/Alberta/48/76 are generally not different from the conditions described for the Fowl-Plague-Virus and for human strains.
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PMID:[Characterization of RNA polymerase activity of highly purified preparations of influenza virus A/duck/Alberta/48/76]. 637 62


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