scholarly journals Influenza Virion-Derived Viral Ribonucleoproteins Synthesize both mRNA and cRNA In Vitro

2006 ◽  
Vol 81 (5) ◽  
pp. 2196-2204 ◽  
Author(s):  
F. T. Vreede ◽  
G. G. Brownlee
Keyword(s):  
Influenza Virus ◽  
Life Cycle ◽  
Rna Polymerase ◽  
Influenza A ◽  
De Novo ◽  
Early Results ◽  
Virus Rna ◽  
Replicative Intermediates ◽  
Viral Genomic Rna

ABSTRACT The mechanisms regulating the synthesis of mRNA, cRNA, and viral genomic RNA (vRNA) by the influenza A virus RNA-dependent RNA polymerase are not fully understood. Early results suggested that the RNA polymerase “switched” from a transcriptase to a replicase during the viral life cycle in response to the expression of viral proteins. However, recently an alternative model suggesting that replication of influenza virus is regulated by stabilization of the replicative intermediates was proposed. According to this model, the virion-associated polymerase is capable of synthesizing both mRNA and cRNA. We now demonstrate that virion-derived viral ribonucleoproteins (vvRNPs) synthesize both mRNA and cRNA in vitro in the absence of non-virion-associated RNA polymerase or nucleoproteins. The authenticity of the in vitro-transcribed mRNA and cRNA was confirmed by terminal sequence analysis. The addition of non-virion-associated polymerase or NP had no effect on vvRNP activity. De novo synthesis of cRNA was found to be more sensitive than the capped primer-dependent synthesis of mRNA to the concentration of ATP, CTP, and GTP. We conclude that vvRNPs intrinsically possess both transcriptase and replicase activities and that there is no switch in the synthesis of mRNA to cRNA during the influenza virus life cycle.

scholarly journals Different De Novo Initiation Strategies Are Used by Influenza Virus RNA Polymerase on Its cRNA and Viral RNA Promoters during Viral RNA Replication

2006 ◽  
Vol 80 (5) ◽  
pp. 2337-2348 ◽  
Author(s):  
Tao Deng ◽  
Frank T. Vreede ◽  
George G. Brownlee
Keyword(s):  
Influenza Virus ◽  
Rna Polymerase ◽  
De Novo ◽  
Viral Rna ◽  
Virus Rna ◽  
Initiation Of Replication ◽  
Replicative Intermediates ◽  
Internal Initiation

ABSTRACT Various mechanisms are used by single-stranded RNA viruses to initiate and control their replication via the synthesis of replicative intermediates. In general, the same virus-encoded polymerase is responsible for both genome and antigenome strand synthesis from two different, although related promoters. Here we aimed to elucidate the mechanism of initiation of replication by influenza virus RNA polymerase and establish whether initiation of cRNA and viral RNA (vRNA) differed. To do this, two in vitro replication assays, which generated transcripts that had 5′ triphosphate end groups characteristic of authentic replication products, were developed. Surprisingly, mutagenesis screening suggested that the polymerase initiated pppApG synthesis internally on the model cRNA promoter, whereas it initiated pppApG synthesis terminally on the model vRNA promoter. The internally synthesized pppApG could subsequently be used as a primer to realign, by base pairing, to the terminal residues of both the model cRNA and vRNA promoters. In vivo evidence, based on the correction of a mutated or deleted residue 1 of a cRNA chloramphenicol acetyltransferase reporter construct, supported this internal initiation and realignment model. Thus, influenza virus RNA polymerase uses different initiation strategies on its cRNA and vRNA promoters. To our knowledge, this is novel and has not previously been described for any viral RNA-dependent RNA polymerase. Such a mechanism may have evolved to maintain genome integrity and to control the level of replicative intermediates in infected cells.

scholarly journals Temperature-Sensitive Mutants in the Influenza A Virus RNA Polymerase: Alterations in the PA Linker Reduce Nuclear Targeting of the PB1-PA Dimer and Result in Viral Attenuation

2015 ◽  
Vol 89 (12) ◽  
pp. 6376-6390 ◽  
Author(s):  
Bruno Da Costa ◽  
Alix Sausset ◽  
Sandie Munier ◽  
Alexandre Ghounaris ◽  
Nadia Naffakh ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Rna Polymerase ◽  
Nuclear Import ◽  
Influenza A ◽  
Rational Design ◽  
Hot Spot ◽  
Temperature Sensitive ◽  
Nuclear Targeting ◽  
Virus Rna ◽  
Endonuclease Domain

ABSTRACTThe influenza virus RNA-dependent RNA polymerase catalyzes genome replication and transcription within the cell nucleus. Efficient nuclear import and assembly of the polymerase subunits PB1, PB2, and PA are critical steps in the virus life cycle. We investigated the structure and function of the PA linker (residues 197 to 256), located between its N-terminal endonuclease domain and its C-terminal structured domain that binds PB1, the polymerase core. Circular dichroism experiments revealed that the PA linker by itself is structurally disordered. A large series of PA linker mutants exhibited a temperature-sensitive (ts) phenotype (reduced viral growth at 39.5°C versus 37°C/33°C), suggesting an alteration of folding kinetic parameters. Thetsphenotype was associated with a reduced efficiency of replication/transcription of a pseudoviral reporter RNA in a minireplicon assay. Using a fluorescent-tagged PB1, we observed thattsand lethal PA mutants did not efficiently recruit PB1 to reach the nucleus at 39.5°C. A protein complementation assay using PA mutants, PB1, and β-importin IPO5 tagged with fragments of theGaussia princepsluciferase showed that increasing the temperature negatively modulated the PA-PB1 and the PA-PB1-IPO5 interactions or complex stability. The selection of revertant viruses allowed the identification of different types of compensatory mutations located in one or the other of the three polymerase subunits. Twotsmutants were shown to be attenuated and able to induce antibodies in mice. Taken together, our results identify a PA domain critical for PB1-PA nuclear import and that is a “hot spot” to engineertsmutants that could be used to design novel attenuated vaccines.IMPORTANCEBy targeting a discrete domain of the PA polymerase subunit of influenza virus, we were able to identify a series of 9 amino acid positions that are appropriate to engineer temperature-sensitive (ts) mutants. This is the first time that a large number oftsmutations were engineered in such a short domain, demonstrating that rational design oftsmutants can be achieved. We were able to associate this phenotype with a defect of transport of the PA-PB1 complex into the nucleus. Reversion substitutions restored the ability of the complex to move to the nucleus. Two of thesetsmutants were shown to be attenuated and able to produce antibodies in mice. These results are of high interest for the design of novel attenuated vaccines and to develop new antiviral drugs.

scholarly journals Role of Initiating Nucleoside Triphosphate Concentrations in the Regulation of Influenza Virus Replication and Transcription

2008 ◽  
Vol 82 (14) ◽  
pp. 6902-6910 ◽  
Author(s):  
Frank T. Vreede ◽  
Hugh Gifford ◽  
George G. Brownlee
Keyword(s):  
Influenza Virus ◽  
Virus Replication ◽  
Influenza A ◽  
De Novo ◽  
Nucleoside Triphosphate ◽  
Ribonucleoprotein Complexes ◽  
Influenza Virus Replication ◽  
High Concentrations

ABSTRACT The mechanisms regulating the synthesis of mRNA, cRNA, and viral genomic RNA (vRNA) by the influenza A virus RNA-dependent RNA polymerase are not fully understood. Previous studies in our laboratory have shown that virion-derived viral ribonucleoprotein complexes synthesize both mRNA and cRNA in vitro and early in the infection cycle in vivo. Our continued studies showed that de novo synthesis of cRNA in vitro is more sensitive to the concentrations of ATP, CTP, and GTP than capped-primer-dependent synthesis of mRNA. Using rescued recombinant influenza A/WSN/33 viruses, we now demonstrate that the 3′-terminal sequence of the vRNA promoter dictates the requirement for a high nucleoside triphosphate (NTP) concentration during de novo-initiated replication to cRNA, whereas this is not the case for the extension of capped primers during transcription to mRNA. In contrast to some other viral polymerases, for which only the initiating NTP is required at high concentrations, influenza virus polymerase requires high concentrations of the first three NTPs. In addition, we show that base pair mutations in the vRNA promoter can lead to nontemplated dead-end mutations during replication to cRNA in vivo. Based on our observations, we propose a new model for the de novo initiation of influenza virus replication.

scholarly journals The mechanism of resistance to favipiravir in influenza

2018 ◽  
Vol 115 (45) ◽  
pp. 11613-11618 ◽  
Author(s):  
Daniel H. Goldhill ◽  
Aartjan J. W. te Velthuis ◽  
Robert A. Fletcher ◽  
Pinky Langat ◽  
Maria Zambon ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Influenza A Virus ◽  
Influenza A ◽  
H1n1 Influenza ◽  
Viral Fitness ◽  
Virus Infections ◽  
Virus Rna ◽  
Evolution Of Resistance ◽  
Emergence Of Resistance

Favipiravir is a broad-spectrum antiviral that has shown promise in treatment of influenza virus infections. While emergence of resistance has been observed for many antiinfluenza drugs, to date, clinical trials and laboratory studies of favipiravir have not yielded resistant viruses. Here we show evolution of resistance to favipiravir in the pandemic H1N1 influenza A virus in a laboratory setting. We found that two mutations were required for robust resistance to favipiravir. We demonstrate that a K229R mutation in motif F of the PB1 subunit of the influenza virus RNA-dependent RNA polymerase (RdRP) confers resistance to favipiravir in vitro and in cell culture. This mutation has a cost to viral fitness, but fitness can be restored by a P653L mutation in the PA subunit of the polymerase. K229R also conferred favipiravir resistance to RNA polymerases of other influenza A virus strains, and its location within a highly conserved structural feature of the RdRP suggests that other RNA viruses might also acquire resistance through mutations in motif F. The mutations identified here could be used to screen influenza virus-infected patients treated with favipiravir for the emergence of resistance.

Mesoionic Heterocyclic Compounds as Candidate Messenger RNA Cap Analogue Inhibitors of the Influenza Virus RNA Polymerase Cap-Binding Activity

2009 ◽  
Vol 19 (5) ◽  
pp. 213-218 ◽  
Author(s):  
Ian Mickleburgh ◽  
Feng Geng ◽  
Laurence Tiley
Keyword(s):  
Influenza Virus ◽  
Rna Polymerase ◽  
Messenger Rna ◽  
Binding Activity ◽  
Endonucleolytic Cleavage ◽  
Virus Rna ◽  
Fused Ring ◽  
Mesoionic Heterocycles ◽  
Potential Inhibitors

Background: An unusual feature of influenza viral messenger RNA (mRNA) synthesis is its dependence upon host cell mRNAs as a source of capped RNA primers. A crucial activity of the influenza polymerase is to steal these primers by binding and cleaving the caps from host mRNAs. The recent structural analysis of the cap-binding fragment of the influenza virus PB2 protein has highlighted the importance of the mesoionic properties of the N7-methylguanine (N7mG) component of the mRNA cap in this interaction. Methods: A series of mesoionic heterocycles with 5,6-fused ring systems analogous to the N7mG component of mRNA cap structures were synthesized and examined for the ability to inhibit the cap-binding activity of the influenza virus RNA polymerase complex using a bead-based in vitro cap-binding assay. Results: None of the compounds tested were able to significantly inhibit binding and subsequent endonucleolytic cleavage of a synthetic radiolabelled capped mRNA substrate by recombinant influenza virus polymerase in vitro. Conclusions: Compounds analogous to the mesoionic N7mG component of mRNA cap structures comprise a large class of potential inhibitors of the influenza virus polymerase. Although this preliminary assessment of a small group of related analogues was unsuccessful, further screening of this class of compounds is warranted.

scholarly journals Codon Deletions in the Influenza A Virus PA Gene Generate Temperature-Sensitive Viruses

2016 ◽  
Vol 90 (7) ◽  
pp. 3684-3693 ◽  
Author(s):  
Léa Meyer ◽  
Alix Sausset ◽  
Laura Sedano ◽  
Bruno Da Costa ◽  
Ronan Le Goffic ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Rna Polymerase ◽  
Influenza A Virus ◽  
Influenza A ◽  
Wild Type Virus ◽  
Deletion Mutants ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Wild Type

ABSTRACTThe influenza virus RNA-dependent RNA polymerase, which is composed of three subunits, PB1, PB2, and PA, catalyzes genome replication and transcription within the cell nucleus. The PA linker (residues 197 to 256) can be altered by nucleotide substitutions to engineer temperature-sensitive (ts), attenuated mutants that display a defect in the transport of the PA–PB1 complex to the nucleus at a restrictive temperature. In this study, we investigated the ability of the PA linker to tolerate deletion mutations for furtherin vitroandin vivocharacterization. Four viable mutants with single-codon deletions were generated; all of them exhibited atsphenotype that was associated with the reduced efficiency of replication/transcription of a pseudoviral reporter RNA in a minireplicon assay. Using fluorescently tagged PB1, we observed that the deletion mutants did not efficiently recruit PB1 to reach the nucleus at a restrictive temperature (39.5°C). Mouse infections showed that the four mutants were attenuated and induced antibodies that were able to protect mice from challenge with a lethal homologous wild-type virus. Serialin vitropassages of two deletion mutants at 39.5°C and 37°C did not allow the restoration of a wild-type phenotype among virus progeny. Thus, our results identify codons that can be deleted in the PA gene to engineer genetically stabletsmutants that could be used to design novel attenuated vaccines.IMPORTANCEIn order to generate genetically stable live influenza A virus vaccines, we constructed viruses with single-codon deletions in a discrete domain of the RNA polymerase PA gene. The four rescued viruses exhibited a temperature-sensitive phenotype that we found was associated with a defect in the transport of the PA–PB1 dimer to the nucleus, where viral replication occurs. Thesetsdeletion mutants were shown to be attenuated and to be able to produce antibodies in mice and to protect them from a lethal challenge. Assays to select revertants that were able to grow efficiently at a restrictive temperature failed, showing that these deletion mutants are genetically more stable than conventional substitution mutants. These results are of interest for the design of genetically stable live influenza virus vaccines.

scholarly journals Enisamium Inhibits SARS-CoV-2 RNA Synthesis

Biomedicines ◽  
2021 ◽  
Vol 9 (9) ◽  
pp. 1254
Author(s):  
Stefano Elli ◽  
Denisa Bojkova ◽  
Marco Bechtel ◽  
Thomas Vial ◽  
David Boltz ◽  
...  
Keyword(s):  
Cell Culture ◽  
Rna Polymerase ◽  
Influenza A ◽  
Rna Synthesis ◽  
Herd Immunity ◽  
Virus Rna ◽  
Independent States ◽  
Dynamics Simulations ◽  
Insight Into

Pandemic SARS-CoV-2 causes a mild to severe respiratory disease called coronavirus disease 2019 (COVID-19). While control of the SARS-CoV-2 spread partly depends on vaccine-induced or naturally acquired protective herd immunity, antiviral strategies are still needed to manage COVID-19. Enisamium is an inhibitor of influenza A and B viruses in cell culture and clinically approved in countries of the Commonwealth of Independent States. In vitro, enisamium acts through metabolite VR17-04 and inhibits the activity of the influenza A virus RNA polymerase. Here we show that enisamium can inhibit coronavirus infections in NHBE and Caco-2 cells, and the activity of the SARS-CoV-2 RNA polymerase in vitro. Docking and molecular dynamics simulations provide insight into the mechanism of action and indicate that enisamium metabolite VR17-04 prevents GTP and UTP incorporation. Overall, these results suggest that enisamium is an inhibitor of SARS-CoV-2 RNA synthesis in vitro.

scholarly journals Attenuation of Influenza A Virus mRNA Levels by Promoter Mutations

1998 ◽  
Vol 72 (8) ◽  
pp. 6283-6290 ◽  
Author(s):  
Ervin Fodor ◽  
Peter Palese ◽  
George G. Brownlee ◽  
Adolfo García-Sastre
Keyword(s):  
Influenza Virus ◽  
Transcription Initiation ◽  
Influenza A ◽  
Reverse Genetics ◽  
Mrna Levels ◽  
Double Mutation ◽  
Ribonucleoprotein Complexes ◽  
Virus Rna ◽  
Infected Cells

ABSTRACT We have engineered influenza A/WSN/33 viruses which have viral RNA (vRNA) segments with altered base pairs in the conserved double-stranded region of their vRNA promoters. The mutations were introduced into the segment coding for the neuraminidase (NA) by using a reverse genetics system. Two of the rescued viruses which share a C-G→A-U double mutation at positions 11 and 12′ at the 3′ and 5′ ends of the NA-specific vRNA, respectively, showed approximately a 10-fold reduction of NA levels. The mutations did not dramatically affect the NA-specific vRNA levels found in virions or the NA-specific vRNA and cRNA levels in infected cells. In contrast, there was a significant decrease in the steady-state levels of NA-specific mRNAs in infected cells. Transcription studies in vitro with ribonucleoprotein complexes isolated from the two transfectant viruses indicated that transcription initiation of the NA-specific segment was not affected. However, the majority of NA-specific transcripts lacked poly(A) tails, suggesting that mutations in the double-stranded region of the influenza virus vRNA promoter can attenuate polyadenylation of mRNA molecules. This is the first time that a promoter mutation in an engineered influenza virus has shown a differential effect on influenza virus RNA transcription and replication.

Effect of anaferon for children on the life cycle of influenza virus A/H1N1

2018 ◽  
pp. 87-94
Author(s):  
А.Г. Емельянова ◽  
М.В. Никифорова ◽  
Е.С. Дон ◽  
Н.Р. Махмудова ◽  
И.Н. Фалынскова ◽  
...  
Keyword(s):  
Influenza Virus ◽  
Life Cycle ◽  
Antiviral Activity ◽  
Influenza A ◽  
Mdck Cells ◽  
Antiviral Effect ◽  
H1n1 Influenza ◽  
Dose Dependence ◽  
Influenza Virus A

Цель исследования - изучение возможного прямого влияния препарата «Анаферон детский» на жизненный цикл вируса гриппа А в процессе развития инфекции, а также дозозависимости противовирусного эффекта in vitro . Методика. Исследование противовирусной активности препарата «Анаферон детский» in vitro было проведено с использованием культуры клеток MDCK (Madin Darby canine kidney) и эталонных штаммов вируса гриппа A (H1N1) pdm09: A/California/07/09 и А/California/04/09, полученных от ВОЗ. Использовались методы оценки подавления Анафероном детским вирусной репликации (по результатам иммуноферментного анализа по определению экспрессии внутренних белков NP и M1 вируса гриппа А) и его влияние на ультраструктурные особенности морфогенеза вируса гриппа методом электронной микроскопии. В качестве положительного контроля был использован Озельтамивир карбоксилат в концентрации 10 мкМ. Для мониторинга валидности экспериментальной модели в работе использовали клетки, зараженные вирусом без добавления экспериментальных образцов (контроль вируса), а также интактные клетки (клеточный контроль). Результаты. В ходе исследования показан дозозависимый противовирусный эффект препарата «Анаферон детский» для 3 тестируемых разведений - 1/8, 1/12, 1/16. Методом электронной микроскопии показано, что применение препарата «Анаферон детский» при сравнении с контрольным образцом влияло на процесс почкования вирионов. Заключение. Впервые показана дозозависимость противовирусного действия препарата «Анаферон детский», а также подтверждена его эффективность в отношении двух штаммов вируса пандемического гриппа А/H1N1. Документировано, что применение препарата «Анаферон детский» нарушает жизненный цикл вируса гриппа А. Механизмы развития такого эффекта требуют дополнительного изучения, однако можно предположить их связь с ИФН-индуцирующими свойствами препарата «Анаферон детский», так как было показано, что в начале лечения вирусной инфекции препарат вызывает индукцию синтеза белков системы интерферонов. The aim of this study was to evaluate a possible direct effect of Anaferon for Children on the life cycle of influenza A virus during infection development and a dose response of the antiviral effect in vitro. Methods. The in vitro antiviral activity of Anaferon for Children was studied on cultured MDCK cells and reference strains of influenza virus A (H1N1) pdm09: A/California/07/09 and A/California/04/09, both from the WHO. Inhibition of viral replication by Anaferon for Children and its effect on ultrastructural features of the influenza morphogenesis were evaluated using electron microscopy. Results. The study demonstrated a dose dependence of Anaferon for Children antiviral activity for three dilutions - 1/8, 1/12, and 1/16. Anaferon for Children affected the process of virion budding as compared to placebo. Conclusion. The study showed that the anti-influenza action of Anaferon for Children was dose-dependent and confirmed that this drug was effective against two strains of pandemic A/H1N1 influenza. Furthermore, Anaferon for children disrupted one or several stages of the virus life cycle.

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