title: Nuclear export of influenza A virus mRNAs requires ongoing RNA polymerase II activity.
abstract: Influenza A virus transcribes its segmented negative sense RNA genome in the nuclei of infected cells in a process long known to require host RNA polymerase II (RNAP-II). RNA polymerase II synthesizes pre-mRNAs whose 5'-cap structures are scavenged by the viral RNA-dependent RNA polymerase during synthesis of viral mRNAs. Drugs that inhibit RNAP-II therefore block viral replication, but not necessarily solely by denying the viral polymerase a source of cap-donor molecules. We show here that 5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole (DRB), a compound that prevents processive transcription by RNAP-II, inhibits expression of the viral HA, M1 and NS1 genes at the post-transcriptional level. Abundant quantities of functionally and structurally intact viral mRNAs are made in the presence of DRB but with the exception of NP and NS2 mRNAs, are not efficiently translated. Taking M1 and NP mRNAs as representatives of DRB-sensitive and insensitive mRNAs, respectively, we found that the block to translation operates at the level of nuclear export. Furthermore, removal of DRB reversed this block unless a variety of chemically and mechanistically distinct RNAP-II inhibitors were added instead. We conclude that influenza A virus replication requires RNAP-II activity not just to provide capped mRNA substrates but also to facilitate nuclear export of selected viral mRNAs.
authors.affiliation: Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK.
authors.forename: Maria-Joao
authors.initials: MJ
authors.lastname: Amorim
authors.forename: Eliot K
authors.initials: EK
authors.lastname: Read
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Dalton
authors.forename: Liz
authors.initials: L
authors.lastname: Medcalf
authors.forename: Paul
authors.initials: P
authors.lastname: Digard
mesh_terms: D021581:Active Transport, Cell Nucleus; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D004004:Dichlororibofuranosylbenzimidazole / Q000494:pharmacology; D004285:Dogs; D015870:Gene Expression / Q000187:drug effects; D005814:Genes, Viral; D006801:Humans; D009980:Influenza A virus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D012319:RNA Polymerase II / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D004004:Dichlororibofuranosylbenzimidazole; D012319:RNA Polymerase II