The nucleus is highly compartmentalized yet dynamic. Subnuclear functions are regulated by controlling the subnuclear localization of the nuclear proteins. Influenza viral ribonucleoprotein (vRNP) is replicated in the nucleus and then exported to the cytoplasm. However, the precise subnuclear localization and transport of vRNPs remain unclear. Here, we show that CLUH, a host protein whose cellular function is not well established, plays a key role in the subnuclear transport of vRNP. Viral PB2 and M1 induced CLUH translocation to the nucleoplasm and SC35-positive speckles, respectively, even though CLUH is usually cytoplasmic. CLUH depletion inhibited the translocation of M1 to SC35-positive speckles, but did not interfere with PB2 localization to the nucleoplasm and disrupted the subnuclear transport of vRNP, abolishing vRNP nuclear export without affecting viral RNA or protein expression. Our findings suggest that CLUH plays a role in the subnuclear transport of progeny vRNP.
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The authors thank E. Takashita (National Institute of Infectious Diseases, Japan) for providing mouse anti-M1 (WS-27/52) and mouse anti-HA (WS3-54) antibodies, T. Kitamura (Institute of Medical Science, University of Tokyo) for providing Plat-GP cells and S. Watson for editing the manuscript. The authors thank T. Noda, E. Kawakami, T. Lopes, J. I-Hsuan Wang, Y. Sakai-Tagawa, K. Iwatsuki-Horimoto and our other co-workers for discussions and technical support. The authors also thank Y. Tomari (a grant-in-aid for Scientific Research on Innovative Areas, ‘Non-coding RNA neo-taxonomy’) for use of the super-resolution microscope and T. Watanabe (Carl Zeiss Microscopy) for help with microscope operation. This research was supported by the Japan Initiative for Global Research Network on Infectious Diseases from the Ministry of Education, Culture, Sports, Science and Technology, Japan, and from the Japan Agency for Medical Research and Development (AMED); by grants-in-aid from the Ministry of Health, Labour and Welfare, Japan; by ERATO; by grants from the Strategic Basic Research Program of the Japan Science and Technology Agency; by the Advanced Research & Development Programs for Medical Innovation from AMED; and by JSPS, KAKENHI grant no. 15K19107. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of this manuscript.
The authors declare no competing financial interests.
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Ando, T., Yamayoshi, S., Tomita, Y. et al. The host protein CLUH participates in the subnuclear transport of influenza virus ribonucleoprotein complexes. Nat Microbiol 1, 16062 (2016). https://doi.org/10.1038/nmicrobiol.2016.62