title: Nucleocapsid protein structures from orthobunyaviruses reveal insight into ribonucleoprotein architecture and RNA polymerization.
abstract: All orthobunyaviruses possess three genome segments of single-stranded negative sense RNA that are encapsidated with the virus-encoded nucleocapsid (N) protein to form a ribonucleoprotein (RNP) complex, which is uncharacterized at high resolution. We report the crystal structure of both the Bunyamwera virus (BUNV) N-RNA complex and the unbound Schmallenberg virus (SBV) N protein, at resolutions of 3.20 and 2.75 Å, respectively. Both N proteins crystallized as ring-like tetramers and exhibit a high degree of structural similarity despite classification into different orthobunyavirus serogroups. The structures represent a new RNA-binding protein fold. BUNV N possesses a positively charged groove into which RNA is deeply sequestered, with the bases facing away from the solvent. This location is highly inaccessible, implying that RNA polymerization and other critical base pairing events in the virus life cycle require RNP disassembly. Mutational analysis of N protein supports a correlation between structure and function. Comparison between these crystal structures and electron microscopy images of both soluble tetramers and authentic RNPs suggests the N protein does not bind RNA as a repeating monomer; thus, it represents a newly described architecture for bunyavirus RNP assembly, with implications for many other segmented negative-strand RNA viruses.
authors.affiliation: School of Molecular and Cellular Biology, University of Leeds, Leeds LS2 9JT, UK.
authors.forename: Antonio
authors.initials: A
authors.lastname: Ariza
authors.forename: Sian J
authors.initials: SJ
authors.lastname: Tanner
authors.forename: Cheryl T
authors.initials: CT
authors.lastname: Walter
authors.forename: Kyle C
authors.initials: KC
authors.lastname: Dent
authors.forename: Dale A
authors.initials: DA
authors.lastname: Shepherd
authors.forename: Weining
authors.initials: W
authors.lastname: Wu
authors.forename: Susan V
authors.initials: SV
authors.lastname: Matthews
authors.forename: Julian A
authors.initials: JA
authors.lastname: Hiscox
authors.forename: Todd J
authors.initials: TJ
authors.lastname: Green
authors.forename: Ming
authors.initials: M
authors.lastname: Luo
authors.forename: Richard M
authors.initials: RM
authors.lastname: Elliott
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Fooks
authors.forename: Alison E
authors.initials: AE
authors.lastname: Ashcroft
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Stonehouse
authors.forename: Neil A
authors.initials: NA
authors.lastname: Ranson
authors.forename: John N
authors.initials: JN
authors.lastname: Barr
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Edwards
mesh_terms: D000595:Amino Acid Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000737:chemistry* / Q000378:metabolism; D016851:Orthobunyavirus / Q000502:physiology; D011485:Protein Binding; D055503:Protein Multimerization; D012313:RNA / Q000737:chemistry* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: C423924:N protein, Bunyamwera bunyavirus; D019590:Nucleocapsid Proteins; D012261:Ribonucleoproteins; D012313:RNA