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Journal of Virology, March 2008, p. 2844-2852, Vol. 82, No. 6
0022-538X/08/$08.00+0     doi:10.1128/JVI.02268-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Geometric Mismatches within the Concentric Layers of Rotavirus Particles: a Potential Regulatory Switch of Viral Particle Transcription Activity{triangledown}

Sonia Libersou,{dagger} Xavier Siebert,{dagger},{ddagger} Malika Ouldali, Leandro F. Estrozi,{ddagger} Jorge Navaza,{ddagger} Annie Charpilienne, Pascale Garnier, Didier Poncet, and Jean Lepault*

Laboratoire de Virologie Moléculaire et Structurale, CNRS, UMR 2472, IFR 115, INRA, UMR 1157, 1 Avenue de la Terrasse, F-91198 Gif-sur-Yvette, France

Received 19 October 2007/ Accepted 26 December 2007

Rotaviruses are prototypical double-stranded RNA viruses whose triple-layered icosahedral capsid constitutes transcriptional machinery activated by the release of the external layer. To understand the molecular basis of this activation, we studied the structural interplay between the three capsid layers by electron cryo-microscopy and digital image processing. Two viral particles and four virus-like particles containing various combinations of inner (VP2)-, middle (VP6)-, and outer (VP7)-layer proteins were studied. We observed that the absence of the VP2 layer increases the particle diameter and changes the type of quasi-equivalent icosahedral symmetry, as described by the shift in triangulation number (T) of the VP6 layer (from T = 13 to T = 19 or more). By fitting X-ray models of VP6 into each reconstruction, we determined the quasi-atomic structures of the middle layers. These models showed that the VP6 lattices, i.e., curvature and trimer contacts, are characteristic of the particle composition. The different functional states of VP6 thus appear as being characterized by trimers having similar conformations but establishing different intertrimeric contacts. Remarkably, the external protein VP7 reorients the VP6 trimers located around the fivefold axes of the icosahedral capsid, thereby shrinking the channel through which mRNA exits the transcribing rotavirus particle. We conclude that the constraints arising from the different geometries imposed by the external and internal layers of the rotavirus capsid constitute a potential switch regulating the transcription activity of the viral particles.

* Corresponding author. Mailing address: Laboratoire de Virologie Moléculaire et Structurale, CNRS, UMR 2472, IFR 115, INRA, UMR 1157, 1 Avenue de la Terrasse, F-91198 Gif-sur-Yvette, France. Phone: (33) 1 69 82 38 55. Fax: (33) 1 69 82 43 08. E-mail: lepault{at}vms.cnrs-gif.fr

{triangledown} Published ahead of print on 9 January 2008.

{dagger} These authors contributed equally to this work.

{ddagger} Present address: Institut de Biologie Structurale, 41, rue Jules Horowitz, F-38027 Grenoble Cedex 1, France.

Journal of Virology, March 2008, p. 2844-2852, Vol. 82, No. 6
0022-538X/08/$08.00+0     doi:10.1128/JVI.02268-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Chen, J. Z., Settembre, E. C., Aoki, S. T., Zhang, X., Bellamy, A. R., Dormitzer, P. R., Harrison, S. C., Grigorieff, N. (2009). From the Cover: Molecular interactions in rotavirus assembly and uncoating seen by high-resolution cryo-EM. Proc. Natl. Acad. Sci. USA 106: 10644-10648 [Abstract] [Full Text]  
  • Rey, F. A. (2009). Single-particle cryoEM reconstructions: Meeting the challenge. Proc. Natl. Acad. Sci. USA 106: 10398-10399 [Full Text]  


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