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Updated: Sep 4, 2026

Affinity Purification of Influenza Virus Ribonucleoprotein Complexes from the Chromatin of Infected Cells
Published on: June 3, 2012
An endonuclease inhibitor unlocks the PA-X shutoff mechanism in influenza A virus
Kohei Oishi1, Kaori Sano1, Seiya Yamayoshi2
1Influenza Research Center, National Institute of Infectious Diseases, Japan Institute for Health Security, Tokyo, Japan; Institute for Vaccine Research and Development, Hokkaido University, Sapporo, Japan.
Abstract:
Influenza A virus protein PA-X mediates host shutoff, yet its molecular mechanism and the role of its C-terminal region remain unclear. When ectopically expressed via plasmids, PA-X cleaves its own mRNAs, leading to remarkably low intracellular expression, which makes its characterization challenging. In this study, we utilize an endonuclease inhibitor to suppress PA-X shutoff activity, enabling its robust expression and purification. Our biochemical analyses reveal that PA-X directly binds RNA via its unique C-terminal basic-rich region and induces mRNA degradation with minimal sequence specificity. Furthermore, we find that while PA-X targets a broad range of RNAs, viral RNAs are protected from its endonuclease activity through their assembly into vRNP complexes. These findings provide critical insights into the PA-X-mediated shutoff strategy, revealing how PA-X modulates the cellular environment while sparing the viral genome to favor viral replication.
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