Structural basis for encapsidation of genomic RNA by La Crosse Orthobunyavirus nucleoprotein.

Abstract

The nucleoprotein (NP) of segmented negative-strand RNA viruses such as Orthomyxo-, Arena-, and Bunyaviruses coats the genomic viral RNA and together with the polymerase forms ribonucleoprotein particles (RNPs), which are both the template for replication and transcription and are packaged into new virions. Here we describe the crystal structure of La Crosse Orthobunyavirus NP both RNA free and a tetrameric form with single-stranded RNA bound. La Crosse Orthobunyavirus NP is a largely helical protein with a fold distinct from other bunyavirus genera NPs. It binds 11 RNA nucleotides in the positively charged groove between its two lobes, and hinged N- and C-terminal arms mediate oligomerization, allowing variable protein-protein interface geometry. Oligomerization and RNA binding are mediated by residues conserved in the Orthobunyavirus genus. In the twofold symmetric tetramer, 44 nucleotides bind in a closed ring with sharp bends at the NP-NP interfaces. The RNA is largely inaccessible within a continuous internal groove. Electron microscopy of RNPs released from virions shows them capable of forming a hierarchy of more or less compact irregular helical structures. We discuss how the planar, tetrameric NP-RNA structure might relate to a polar filament that upon supercoiling could be packaged into virions. This work gives insight into the RNA encapsidation and protection function of bunyavirus NP, but also highlights the need for dynamic rearrangements of the RNP to give the polymerase access to the template RNA.

• Authors: Juan Reguera, Hélène Malet, Friedemann Weber, Stephen Cusack
• Journal: Proceedings of the National Academy of Sciences of the United States of America (Proc Natl Acad Sci U S A) Vol. 110 Issue 18 Pg. 7246-51 (Apr 30 2013) ISSN: 1091-6490 [Electronic] United States
• PMID: 23589854 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Nucleoproteins
• RNA, Viral
• Recombinant Proteins

Topics

• Amino Acid Sequence
• Capsid (chemistry)
• Genome, Viral (genetics)
• La Crosse virus (chemistry, genetics, ultrastructure)
• Models, Molecular
• Molecular Sequence Data
• Nucleoproteins (chemistry, isolation & purification, ultrastructure)
• Protein Structure, Secondary
• RNA, Viral (chemistry, genetics, ultrastructure)
• Recombinant Proteins (chemistry, isolation & purification)
• Sequence Alignment