Influenza A virus is a pathogen of great medical impact. To develop novel antiviral strategies, it is essential to understand the molecular aspects of virus–host cell interactions in detail. During entry, the viral ribonucleoproteins (vRNPs) that carry the RNA genome must be released from the incoming particle before they can enter the nucleus for replication. The uncoating process is facilitated by histone deacetylase 6 (ref.1). However, the precise mechanism of shell opening and vRNP debundling is unknown. Here, we show that transportin 1, a member of the importin-β family proteins, binds to a PY-NLS2 sequence motif close to the amino terminus of matrix protein (M1) exposed during acid priming of the viral core. It promotes the removal of M1 and induces disassembly of vRNP bundles. Next, the vRNPs interact with importin-α/β and enter the nucleus. Thus, influenza A virus uses dual importin-βs for distinct steps in host cell entry.
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The data that support the findings of this study are available from the corresponding author upon request. Atomic coordinates and structure factors of G18A M1-N have been deposited in the Protein Data Bank under accession code 6I3H.
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We thank T. Wild for help with siRNA screen preparation, D. Alibhai for image analysis, T. Schwarz for super-resolution microscopy and E. Onischenko for protein purification. This work was supported by the European Research Council (2-73905-09, Cellular biology of virus infection to A.H.); and the Swiss National Science Foundation (2-77478-12, Regulation of early to late endosomal traffic to A.H.; 31003A 166565, NCCR RNA&Disease to U.K.; and SystemsX VirX—a host-directed approach against viral disease to Y.Y. and H.G.). The Friedrich Miescher Institute for Biomedical Research is supported by the Novartis Research Foundation (J.K. and H.G.). Y.M. was funded by the Japan Society for the Promotion of Science (Research Fellowship for Young Scientists). Part of this work was performed at beamline X10SA of the Swiss Light Source.
The authors declare no competing interests.
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Miyake, Y., Keusch, J.J., Decamps, L. et al. Influenza virus uses transportin 1 for vRNP debundling during cell entry. Nat Microbiol 4, 578–586 (2019). https://doi.org/10.1038/s41564-018-0332-2
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