The structure of immature virus like Rous sarcoma virus gag particles reveals a structural role for the p10 domain in assembly Journal Article

Author(s): Schur, Florian; Dick, Robert A; Hagen, Wim J; Vogt, Volker M; Briggs, John A
Article Title: The structure of immature virus like Rous sarcoma virus gag particles reveals a structural role for the p10 domain in assembly
Abstract: The polyprotein Gag is the primary structural component of retroviruses. Gag consists of independently folded domains connected by flexible linkers. Interactions between the conserved capsid (CA) domains of Gag mediate formation of hexameric protein lattices that drive assembly of immature virus particles. Proteolytic cleavage of Gag by the viral protease (PR) is required for maturation of retroviruses from an immature form into an infectious form. Within the assembled Gag lattices of HIV-1 and Mason- Pfizer monkey virus (M-PMV), the C-terminal domain of CA adopts similar quaternary arrangements, while the N-terminal domain of CA is packed in very different manners. Here, we have used cryo-electron tomography and subtomogram averaging to study in vitro-assembled, immature virus-like Rous sarcoma virus (RSV) Gag particles and have determined the structure of CA and the surrounding regions to a resolution of ~8 Å. We found that the C-terminal domain of RSV CA is arranged similarly to HIV-1 and M-PMV, whereas the N-terminal domain of CA adopts a novel arrangement in which the upstream p10 domain folds back into the CA lattice. In this position the cleavage site between CA and p10 appears to be inaccessible to PR. Below CA, an extended density is consistent with the presence of a six-helix bundle formed by the spacer-peptide region. We have also assessed the affect of lattice assembly on proteolytic processing by exogenous PR. The cleavage between p10 and CA is indeed inhibited in the assembled lattice, a finding consistent with structural regulation of proteolytic maturation.
Journal Title: Journal of Virology
Volume: 89
Issue 20
ISSN: 1098-5514
Publisher: ASM  
Date Published: 2015-01-01
Start Page: 10294
End Page: 10302
DOI: 10.1128/JVI.01502-15
Notes: This study was supported by a grant from the Deutsche Forschungsgemeinschaft to J.A.G.B. (BR 3635/2-1) and by USPHS grant GM-107013 to V.M.V. We thank members of the Briggs group for helpful discussions. The Briggs laboratory acknowledges financial support from the European Molecular Biology Laboratory and the Chica und Heinz Schaller Stiftung. This study was technically supported by EMBL IT services.
Open access: no