Deng Tao, Engelhardt Othmar G, Thomas Benjamin, Akoulitchev Alexandre V, Brownlee George G, Fodor Ervin
Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford OX1 3RE, United Kingdom.
J Virol. 2006 Dec;80(24):11911-9. doi: 10.1128/JVI.01565-06. Epub 2006 Sep 27.
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.
甲型流感病毒RNA依赖性RNA聚合酶是一种由聚合酶碱性蛋白1（PB1）、PB2和聚合酶酸性蛋白（PA）亚基组成的异源三聚体复合物。它在受感染细胞的细胞核中进行病毒RNA基因组的转录和复制。我们已鉴定出一种核输入因子，即Ran结合蛋白5（RanBP5），也称为核转运蛋白β3、输入蛋白β3或输入蛋白5，它是PB1亚基的相互作用蛋白。RanBP5单独与PB1相互作用，或与PB1-PA二聚体相互作用，但不与PB1-PB2二聚体或三聚体复合物相互作用。RanBP5与PB1-PA之间的相互作用在体外被RanGTP破坏，从而使PB2能够与PB1-PA二聚体结合形成功能性三聚体RNA聚合酶复合物。我们提出了一个模型，其中RanBP5通过将PB1-PA二聚体靶向细胞核，作为新合成聚合酶的输入因子。与该模型一致，小干扰RNA（siRNA）介导的RanBP5敲低抑制了PB1-PA二聚体的核积累。此外，RanBP5的siRNA敲低导致受感染细胞中病毒RNA的积累延迟，证实RanBP5在流感病毒生命周期中发挥生物学作用。
