title: Replication-coupled and host factor-mediated encapsidation of the influenza virus genome by viral nucleoprotein.
abstract: The influenza virus RNA-dependent RNA polymerase is capable of initiating replication but mainly catalyzes abortive RNA synthesis in the absence of viral and host regulatory factors. Previously, we reported that IREF-1/minichromosome maintenance (MCM) complex stimulates a de novo initiated replication reaction by stabilizing an initiated replication complex through scaffolding between the viral polymerase and nascent cRNA to which MCM binds. In addition, several lines of genetic and biochemical evidence suggest that viral nucleoprotein (NP) is involved in successful replication. Here, using cell-free systems, we have shown the precise stimulatory mechanism of virus genome replication by NP. Stepwise cell-free replication reactions revealed that exogenously added NP free of RNA activates the viral polymerase during promoter escape while it is incapable of encapsidating the nascent cRNA. However, we found that a previously identified cellular protein, RAF-2p48/NPI-5/UAP56, facilitates replication reaction-coupled encapsidation as an NP molecular chaperone. These findings demonstrate that replication of the virus genome is followed by its encapsidation by NP in collaboration with its chaperone.
authors.affiliation: Department of Infection Biology, Graduate School of Comprehensive Human Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba 305-8575, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kawaguchi
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Momose
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Nagata
mesh_terms: D002213:Capsid / Q000378:metabolism*; D002474:Cell-Free System / Q000378:metabolism; D053487:DEAD-box RNA Helicases / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D016679:Genome, Viral; D006367:HeLa Cells; D006801:Humans; D009980:Influenza A virus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D019590:Nucleocapsid Proteins; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D014758:Viral Core Proteins / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication
chemical_list: D018832:Molecular Chaperones; C048842:NP protein, Influenza A virus; D019590:Nucleocapsid Proteins; D012367:RNA, Viral; D016601:RNA-Binding Proteins; D014758:Viral Core Proteins; C487886:DDX39B protein, human; D053487:DEAD-box RNA Helicases