Structure of Schmallenberg orthobunyavirus nucleoprotein suggests a novel mechanism of genome encapsidation
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Schmallenberg virus (SBV), a newly emerged orthobunyavirus (family Bunyaviridae), has spread rapidly across Europe and has caused congenital abnormalities in the offspring of cattle, sheep, and goats. Like other orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that encodes four structural and two nonstructural proteins. The nucleoprotein (N) encapsidates the three viral genomic RNA segments and plays a crucial role in viral RNA transcription and replication. Here we report the crystal structure of the bacterially expressed SBV nucleoprotein to a 3.06-angstrom resolution. The protomer is composed of two domains (N-terminal and C-terminal domains) with flexible N-terminal and C-terminal arms. The N protein has a novel fold and forms a central positively charged cleft for genomic RNA binding. The nucleoprotein purified under native conditions forms a tetramer, while the nucleoprotein obtained following denaturation and refolding forms a hexamer. Our structural and functional analyses demonstrate that both N-terminal and C-terminal arms are involved in N-N interaction and oligomerization and play an essential role in viral RNA synthesis, suggesting a novel mechanism for viral RNA encapsidation and transcription.
Dong , H , Li , P , Elliott , R M & Dong , C 2013 , ' Structure of Schmallenberg orthobunyavirus nucleoprotein suggests a novel mechanism of genome encapsidation ' Journal of Virology , vol 87 , no. 10 , pp. 5593-5601 . DOI: 10.1128/JVI.00223-13
Journal of Virology
Copyright © 2013, American Society for Microbiology. All Rights Reserved.
This work was supported by the Medical Research Council (grant no. G1100110/1 to C.D.) and the Wellcome Trust (career development fellowship WT083501MA to C.D. and program grant 079810 and project grant 091783 to R.M.E.). R.M.E. is a Wellcome Trust senior investigator.
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