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Intracellular localization of influenza C virus NS2 protein (NEP) in infected cells and its incorporation into virions

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Abstract

RNA segment 7 of influenza C virus encodes two non-structural (NS) proteins, NS1 and NS2. The influenza C virus NS2 protein has been proposed to possess nuclear export activity like that of influenza A and B virus NS2 proteins (NEP). In the present study, we investigated the kinetics and localization of the NS2 protein in influenza C virus-infected cells, and analysed whether NS2 is present in virions. Immunofluorescent staining analysis of the infected cells indicated that NS2 was localized in the nucleus immediately after synthesis and predominantly in the cytoplasm in the later stages of infection. Confocal microscopy revealed that a part of the NS2 protein was colocalized with nucleoprotein NP/vRNP in the cytoplasm and on the cell membrane in the late stages of infection. The NS2 protein was detected in influenza C virions purified by gradient centrifugations and/or affinity chromatography. Trypsin treatment demonstrated that the NS2 protein was present inside the viral envelope. Furthermore, glycerol gradient analysis of detergent-solubilized virions revealed that the NS2 protein cosedimented with vRNPs. These data suggest that the influenza C virus NS2 protein is incorporated into virions, where it associates with vRNP.

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Acknowledgments

This paper is dedicated to the memory of Prof. Kiyoto Nakamura. This work was supported in part by the grant provided by the Ichiro Kanehara Foundation, Takeda Science Foundation, TERUMO LIFE SCIENCE FOUNDATION and a Grant-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science and Technology, Japan.

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  1. Yoshihiko Kohno

    Present address: Drug Analysis Division, Kashima Laboratory, Mitsubishi Chemical Safety Institute Ltd, Sunayama 14, Kamisu, Ibaraki, 314-0255, Japan

Authors and Affiliations

  1. Department of Bacteriology, Faculty of Medicine, Yamagata University, Iida-Nishi, Yamagata, 990-9585, Japan

    Yoshihiko Kohno, Yasushi Muraki, Yoko Matsuzaki, Emi Takashita, Kanetsu Sugawara & Seiji Hongo

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  1. Yoshihiko Kohno
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  2. Yasushi Muraki
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  3. Yoko Matsuzaki
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  4. Emi Takashita
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  5. Kanetsu Sugawara
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  6. Seiji Hongo
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Correspondence to Seiji Hongo.

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Kohno, Y., Muraki, Y., Matsuzaki, Y. et al. Intracellular localization of influenza C virus NS2 protein (NEP) in infected cells and its incorporation into virions. Arch Virol 154, 235–243 (2009). https://doi.org/10.1007/s00705-008-0292-6

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  • DOI: https://doi.org/10.1007/s00705-008-0292-6

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