title: Role of ran binding protein 5 in nuclear import and assembly of the influenza virus RNA polymerase complex.
abstract: The influenza A virus RNA-dependent RNA polymerase is a heterotrimeric complex of polymerase basic protein 1 (PB1), PB2, and polymerase acidic protein (PA) subunits. It performs transcription and replication of the viral RNA genome in the nucleus of infected cells. We have identified a nuclear import factor, Ran binding protein 5 (RanBP5), also known as karyopherin beta3, importin beta3, or importin 5, as an interactor of the PB1 subunit. RanBP5 interacted with either PB1 alone or with a PB1-PA dimer but not with a PB1-PB2 dimer or the trimeric complex. The interaction between RanBP5 and PB1-PA was disrupted by RanGTP in vitro, allowing PB2 to bind to the PB1-PA dimer to form a functional trimeric RNA polymerase complex. We propose a model in which RanBP5 acts as an import factor for the newly synthesized polymerase by targeting the PB1-PA dimer to the nucleus. In agreement with this model, small interfering RNA (siRNA)-mediated knock-down of RanBP5 inhibited the nuclear accumulation of the PB1-PA dimer. Moreover, siRNA knock-down of RanBP5 resulted in the delayed accumulation of viral RNAs in infected cells, confirming that RanBP5 plays a biological role during the influenza virus life cycle.
authors.affiliation: Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom.
authors.forename: Tao
authors.initials: T
authors.lastname: Deng
authors.forename: Othmar G
authors.initials: OG
authors.lastname: Engelhardt
authors.forename: Benjamin
authors.initials: B
authors.lastname: Thomas
authors.forename: Alexandre V
authors.initials: AV
authors.lastname: Akoulitchev
authors.forename: George G
authors.initials: GG
authors.lastname: Brownlee
authors.forename: Ervin
authors.initials: E
authors.lastname: Fodor
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D017931:DNA Primers; D012321:DNA-Directed RNA Polymerases / Q000096:biosynthesis*; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D009980:Influenza A virus / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D011485:Protein Binding; D034622:RNA Interference; D017422:Sequence Analysis, DNA; D014764:Viral Proteins / Q000096:biosynthesis*; D028961:beta Karyopherins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D017931:DNA Primers; C107940:IPO5 protein, human; D014764:Viral Proteins; D028961:beta Karyopherins; D012321:DNA-Directed RNA Polymerases