Transcription and replication of the influenza a virus genome.
The genome of influenza A virus consists of eight segments of negative-strand viral RNA (vRNA). During the replication cycle of the virus, the genomic vRNA is transcribed into positive-strand mRNA and complementary RNA (cRNA) in the cell nucleus. The promoter for the synthesis of mRNA molecules is located in a partially double-stranded RNA structure formed by the 5'- and 3'-terminal sequences of genomic vRNA segments. The virus encoded RNA-dependent RNA polymerase complex has to interact with both ends of the vRNA in order to generate capped RNA primers by endonucleolytic cleavage of cellular pre-mRNAs for the initiation of viral mRNA synthesis. Conserved sequence elements in the 5'-end, e.g. a polymerase binding site and a U(5-7) sequence are required for polyadenylation of virus-specific mRNAs. Polyadenylation occurs by reiterative copying of the U(5-7) sequence by the viral RNA polymerase, which is bound to the 5'end of the vRNA template. The U(5-7) sequence acts directly as a template for the poly(A)-tail. During the replication cycle of the virus, a "switch" from mRNA to cRNA synthesis occurs, but the mechanism by which this switch occurs remains unclear. The viral nucleoprotein and its interaction with the polymerase proteins and vRNA might play a role in this process. In contrast to transcription, the process of replication--the synthesis of cRNA and vRNA, which are known to occur in the absence of primers--is poorly understood.
Mikulásová
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Institute of Virology, Slovak Academy of Sciences, Bratislava, Slovak Republic.
Varecková
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Fodor
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D000818:Animals; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D016679:Genome, Viral; D006801:Humans; D009980:Influenza A virus / Q000235:genetics*; D018075:RNA, Complementary / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D014779:Virus Replication
D018075:RNA, Complementary; D012333:RNA, Messenger; D012367:RNA, Viral; D012321:DNA-Directed RNA Polymerases