The Hexamer Structure of the Rift Valley Fever Virus Nucleoprotein Suggests a Mechanism for its Assembly into Ribonucleoprotein Complexes

PLoS Pathogens

Thomas Walz¹  Violaine Lantez¹  François Ferron¹  Rémi Charrel¹  Julien Lescar²  Zongli Li²  Dahai Luo²  Eric I. Danek³  Yeehwa Wong⁴  Bruno Coutard⁴  Bruno Canard⁵ 

[1] Architecture et Fonction des Macromolécules Biologiques, Marseille, France;Harvard Medical School, Department of Cell Biology, Boston, Massachusetts, United States of America;Howard Hughes Medical Institute, Harvard Medical School, Boston, Massachusetts, United States of America;Nanyang Technological University, School of Biological Sciences, Singapore;Unité des Virus Emergents, Université Aix-Marseille II et Institut de Recherche pour le Développement, Marseille, France

关键词: Crystal structure;    Rift Valley fever virus;    Oligomers;    RNA structure;    Protein structure;    RNA-binding proteins;    Crystals;    Viral structure;   

DOI  :  10.1371/journal.ppat.1002030

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Rift Valley fever virus (RVFV), a Phlebovirus with a genome consisting of three single-stranded RNA segments, is spread by infected mosquitoes and causes large viral outbreaks in Africa. RVFV encodes a nucleoprotein (N) that encapsidates the viral RNA. The N protein is the major component of the ribonucleoprotein complex and is also required for genomic RNA replication and transcription by the viral polymerase. Here we present the 1.6 Å crystal structure of the RVFV N protein in hexameric form. The ring-shaped hexamers form a functional RNA binding site, as assessed by mutagenesis experiments. Electron microscopy (EM) demonstrates that N in complex with RNA also forms rings in solution, and a single-particle EM reconstruction of a hexameric N-RNA complex is consistent with the crystallographic N hexamers. The ring-like organization of the hexamers in the crystal is stabilized by circular interactions of the N terminus of RVFV N, which forms an extended arm that binds to a hydrophobic pocket in the core domain of an adjacent subunit. The conformation of the N-terminal arm differs from that seen in a previous crystal structure of RVFV, in which it was bound to the hydrophobic pocket in its own core domain. The switch from an intra- to an inter-molecular interaction mode of the N-terminal arm may be a general principle that underlies multimerization and RNA encapsidation by N proteins from Bunyaviridae. Furthermore, slight structural adjustments of the N-terminal arm would allow RVFV N to form smaller or larger ring-shaped oligomers and potentially even a multimer with a super-helical subunit arrangement. Thus, the interaction mode between subunits seen in the crystal structure would allow the formation of filamentous ribonucleocapsids in vivo. Both the RNA binding cleft and the multimerization site of the N protein are promising targets for the development of antiviral drugs.

【 授权许可】

CC BY