Influenza A virus nucleoprotein (NP) is a structural component that encapsulates the viral genome into the form of ribonucleoprotein complexes (vRNPs). Efficient assembly of vRNPs is critical for the virus life cycle. The assembly route from RNA-free NP to the NP-RNA polymer in vRNPs has been suggested to require a cellular factor UAP56, but the mechanism is poorly understood. Here, we characterized the interaction between NP and UAP56 using recombinant proteins and showed that UAP56 features two NP binding sites. In addition to the UAP56 core comprised of two RecA domains, we identified the N-terminal extension (NTE) of UAP56 as a previously unknown NP binding site. In particular, UAP56-NTE recognizes the nucleic acid binding region of NP. This corroborates our observation that binding of UAP56-NTE and RNA to NP is mutually exclusive. Collectively, our results reveal the molecular basis for how UAP56 acts on RNA-free NP, and provide new insights into NP-mediated influenza genome packaging.
Keywords: DEAD-Box ATPase; Host-pathogen interaction; Influenza A virus; RNA-Binding protein; mRNA nuclear export.
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Conflict of interest statement
Declaration of competing interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Cellular splicing factor UAP56 stimulates trimeric NP formation for assembly of functional influenza viral ribonucleoprotein complexes.Sci Rep. 2017 Oct 25;7(1):14053. doi: 10.1038/s41598-017-13784-4. Sci Rep. 2017. PMID: 29070793 Free PMC article.
The cellular RNA helicase UAP56 is required for prevention of double-stranded RNA formation during influenza A virus infection.J Virol. 2011 Sep;85(17):8646-55. doi: 10.1128/JVI.02559-10. Epub 2011 Jun 15. J Virol. 2011. PMID: 21680511 Free PMC article.
The Cellular DExD/H-Box RNA Helicase UAP56 Co-localizes With the Influenza A Virus NS1 Protein.Front Microbiol. 2018 Sep 12;9:2192. doi: 10.3389/fmicb.2018.02192. eCollection 2018. Front Microbiol. 2018. PMID: 30258431 Free PMC article.
[Dynamics of the influenza virus genome regulated by cellular host factors].Uirusu. 2017;67(1):59-68. doi: 10.2222/jsv.67.59. Uirusu. 2017. PMID: 29593154 Review. Japanese.
UAP56- a key player with surprisingly diverse roles in pre-mRNA splicing and nuclear export.BMB Rep. 2009 Apr 30;42(4):185-8. doi: 10.5483/bmbrep.2009.42.4.185. BMB Rep. 2009. PMID: 19403039 Review.