Architecture of ribonucleoprotein complexes in influenza A virus particles (original) (raw)

Nature volume 439, pages 490–492 (2006)Cite this article

Abstract

In viruses, as in eukaryotes, elaborate mechanisms have evolved to protect the genome and to ensure its timely replication and reliable transmission to progeny. Influenza A viruses are enveloped, spherical or filamentous structures, ranging from 80 to 120 nm in diameter1. Inside each envelope is a viral genome consisting of eight single-stranded negative-sense RNA segments of 890 to 2,341 nucleotides each1. These segments are associated with nucleoprotein and three polymerase subunits, designated PA, PB1 and PB2; the resultant ribonucleoprotein complexes (RNPs) resemble a twisted rod (10–15 nm in width and 30–120 nm in length) that is folded back and coiled on itself2,3,4. Late in viral infection, newly synthesized RNPs are transported from the nucleus to the plasma membrane, where they are incorporated into progeny virions capable of infecting other cells. Here we show, by transmission electron microscopy of serially sectioned virions, that the RNPs of influenza A virus are organized in a distinct pattern (seven segments of different lengths surrounding a central segment). The individual RNPs are suspended from the interior of the viral envelope at the distal end of the budding virion and are oriented perpendicular to the budding tip. This finding argues against random incorporation of RNPs into virions5, supporting instead a model in which each segment contains specific incorporation signals that enable the RNPs to be recruited and packaged as a complete set6,7,8,9,10,11,12. A selective mechanism of RNP incorporation into virions and the unique organization of the eight RNP segments may be crucial to maintaining the integrity of the viral genome during repeated cycles of replication.

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Acknowledgements

We thank J. Gilbert for editing the manuscript; M. Imai, Y. Muramoto and K. Fujii for discussion; Y. Hirata, K. Aoyama and K. Inoke for technical assistance with electron microscopic tomography; and Y. Kawaoka for illustrations. This work was supported by CREST (Japan Science and Technology Agency), by Grants-in-Aid by the Ministry of Education, Culture, Sports, Science and Technology, by the Ministry of Health, Labor and Welfare, Japan, and by a National Institute of Allergy and Infectious Disease Public Health Service research grant (to Y.K.); and by Swedish Research Council grants and the STINT Foundation (to R.H.C.). T.N. was the recipient of a fellowship from the incorporated foundation SYOUSHISYA and a research fellowship from the Japan Society for the Promotion of Science for Young Scientists.

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Author notes

  1. Ayato Takada
    Present address: Research Center for Zoonosis Control, Hokkaido University, Kita-ku, Sapporo, 060-0818, Japan

Authors and Affiliations

  1. Internal Research Center for Infectious Diseases, Institute of Medical Science, University of Tokyo, 108-8639, Shirokanedai, Minato-ku, Tokyo, Japan
    Takeshi Noda & Yoshihiro Kawaoka
  2. Laboratory of Microbiology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, 060-0818, Kita-ku, Sapporo, Japan
    Takeshi Noda & Hiroshi Kida
  3. Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, 332-0012, Saitama, Kawaguchi, Japan
    Takeshi Noda, Ayato Takada & Yoshihiro Kawaoka
  4. Fine Morphology Laboratory, Department of Basic Medical Science, and Division of Virology, Institute of Medical Science, University of Tokyo, 108-8639, Shirokanedai, Minato-ku Tokyo, Japan
    Hiroshi Sagara
  5. Department of Biosciences, Karolinska Institute, 141 57, Huddinge, Sweden
    Albert Yen & R. Holland Cheng
  6. Department of Microbiology and Immunology, Institute of Medical Science, University of Tokyo, 108-8639, Shirokanedai, Minato-ku, Tokyo, Japan
    Ayato Takada & Yoshihiro Kawaoka
  7. Molecular and Cellular Biology, University of California, California, 95616, Davis, USA
    R. Holland Cheng
  8. Department of Pathological Science, School of Veterinary Medicine, University of Wisconsin-Madison, Wisconsin, 53706, Madison, USA
    Yoshihiro Kawaoka

Authors

  1. Takeshi Noda
  2. Hiroshi Sagara
  3. Albert Yen
  4. Ayato Takada
  5. Hiroshi Kida
  6. R. Holland Cheng
  7. Yoshihiro Kawaoka

Corresponding author

Correspondence toYoshihiro Kawaoka.

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Reprints and permissions information is available at npg.nature.com/reprintsandpermissions. The authors declare no competing financial interests.

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Noda, T., Sagara, H., Yen, A. et al. Architecture of ribonucleoprotein complexes in influenza A virus particles.Nature 439, 490–492 (2006). https://doi.org/10.1038/nature04378

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Editorial Summary

Flu virus: pieces of eight

The influenza virus is unusual in that its genome is fragmented, and the mechanism that reconstitutes the genome in viral progeny is largely unknown. A new electron microscopy study reveals that each budding influenza virus particle contains a central rod of genetic material, surrounded by seven peripheral rods in a reproducible pattern. Prior to this work it was commonly thought that viral particles consisted of eight randomly selected RNA segments. This high level of organization could be a weak point in the virus's defences that might be exploited by new antiviral drugs.