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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.

SUBMITTER: Deng T

PROVIDER: S-EPMC1676300 | biostudies-literature | 2006 Dec

REPOSITORIES: biostudies-literature

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Role of ran binding protein 5 in nuclear import and assembly of the influenza virus RNA polymerase complex.

Deng Tao T Engelhardt Othmar G OG Thomas Benjamin B Akoulitchev Alexandre V AV Brownlee George G GG Fodor Ervin E

Journal of virology 20060927 24

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 ...[more]

PMID: 17005651

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Project description:Influenza viruses encode a viral RNA-dependent RNA polymerase (FluPol), which is responsible for transcribing and replicating the negative-sense viral RNA (vRNA) genome. FluPol transcribes vRNA using a host-capped mRNA primer and replicates it by synthesizing a positive-sense cRNA intermediate, which is copied back into vRNA. To carry out these functions, FluPol interacts with vRNA and cRNA using conserved promoter elements at the 5' and 3' termini. Recent structural studies have identified a new surface binding site for the 3' vRNA and cRNA promoters on FluPol, referred to as the mode B site. However, the role of this binding site in FluPol function is unknown. In this study, we used a combination of cell-based and biochemical assays to show that the mode B site is important for both viral genome transcription and replication in influenza A virus. Furthermore, we show that the mode B site is not needed for initiating transcription in vitro but is required to synthesize a full-length product. This is consistent with a model in which the 3' terminus of the vRNA template binds in the mode B site during elongation. Our data provide the first functional insights into the role of the mode B site on FluPol, which advances our understanding of FluPol function and influenza virus replication.IMPORTANCE Influenza viruses are responsible for up to 650,000 deaths per year through seasonal epidemics, and pandemics have caused tens of millions of deaths in the past. Most current therapeutics suffer from widespread resistance, creating a need for new drug targets against influenza virus. The virus encodes an RNA-dependent RNA polymerase, which replicates and transcribes the vRNA genome. The polymerase interacts with vRNA and the complementary replicative intermediate cRNA using several specific binding sites; however, the functions associated with these binding sites remain unknown. Here, we functionally characterize a binding site for the 3' vRNA and cRNA promoters. Our data offer insight into the mechanism of viral genome transcription by the influenza virus polymerase and may be applicable to other related viruses.

Dataset Information

Role of ran binding protein 5 in nuclear import and assembly of the influenza virus RNA polymerase complex.

Publications

Role of ran binding protein 5 in nuclear import and assembly of the influenza virus RNA polymerase complex.

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