Crystal structure of Schmallenberg orthobunyavirus nucleoprotein–RNA complex reveals a novel RNA sequestration mechanism
- 1Biomedical Research Centre, Norwich Medical School, University of East Anglia, Norwich Research Park NR4 7TJ, United Kingdom
- 2Biomedical Sciences Research Complex, School of Biology, University of St Andrews, St Andrews KY16 9ST, United Kingdom
- 3School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
-
↵4 These authors contributed equally to this work.
Abstract
Schmallenberg virus (SBV) is a newly emerged orthobunyavirus (family Bunyaviridae) that has caused severe disease in the offspring of farm animals across Europe. Like all orthobunyaviruses, SBV contains a tripartite negative-sense RNA genome that is encapsidated by the viral nucleocapsid (N) protein in the form of a ribonucleoprotein complex (RNP). We recently reported the three-dimensional structure of SBV N that revealed a novel fold. Here we report the crystal structure of the SBV N protein in complex with a 42-nt-long RNA to 2.16 Å resolution. The complex comprises a tetramer of N that encapsidates the RNA as a cross-shape inside the protein ring structure, with each protomer bound to 11 ribonucleotides. Eight bases are bound in the positively charged cleft between the N- and C-terminal domains of N, and three bases are shielded by the extended N-terminal arm. SBV N appears to sequester RNA using a different mechanism compared with the nucleoproteins of other negative-sense RNA viruses. Furthermore, the structure suggests that RNA binding results in conformational changes of some residues in the RNA-binding cleft and the N- and C-terminal arms. Our results provide new insights into the novel mechanism of RNA encapsidation by orthobunyaviruses.
Keywords
- Schmallenberg virus
- orthobunyavirus
- bunyavirus
- nucleoprotein structure
- RNA replication and transcription
Footnotes
-
↵6 Corresponding authors
E-mail C.Dong{at}uea.ac.uk
E-mail richard.elliott{at}glasgow.ac.uk
- Received March 15, 2013.
- Accepted May 31, 2013.
- © 2013; Published by Cold Spring Harbor Laboratory Press for the RNA Society
This article is distributed exclusively by the RNA Society for the first 12 months after the full-issue publication date (see http://rnajournal.cshlp.org/site/misc/terms.xhtml). After 12 months, it is available under a Creative Commons License (Attribution-NonCommercial 3.0 Unported), as described at http://creativecommons.org/licenses/by-nc/3.0/.