RNA genome packaging and capsid assembly of bluetongue virus visualized in host cells

Xian Xia; Po-Yu Sung; Michael W Martynowycz; Tamir Gonen; Polly Roy; Z Hong Zhou

doi:10.1016/j.cell.2024.03.007

RNA genome packaging and capsid assembly of bluetongue virus visualized in host cells

Cell. 2024 Apr 25;187(9):2236-2249.e17. doi: 10.1016/j.cell.2024.03.007. Epub 2024 Apr 12.

Authors

Xian Xia¹, Po-Yu Sung², Michael W Martynowycz³, Tamir Gonen³, Polly Roy², Z Hong Zhou⁴

Affiliations

¹ Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
² Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK.
³ Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA.
⁴ Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA. Electronic address: hong.zhou@ucla.edu.

PMID: 38614100
DOI: 10.1016/j.cell.2024.03.007

Abstract

Unlike those of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and ssRNA viruses, the mechanism of genome packaging of dsRNA viruses is poorly understood. Here, we combined the techniques of high-resolution cryoelectron microscopy (cryo-EM), cellular cryoelectron tomography (cryo-ET), and structure-guided mutagenesis to investigate genome packaging and capsid assembly of bluetongue virus (BTV), a member of the Reoviridae family of dsRNA viruses. A total of eleven assembly states of BTV capsid were captured, with resolutions up to 2.8 Å, with most visualized in the host cytoplasm. ATPase VP6 was found underneath the vertices of capsid shell protein VP3 as an RNA-harboring pentamer, facilitating RNA packaging. RNA packaging expands the VP3 shell, which then engages middle- and outer-layer proteins to generate infectious virions. These revealed "duality" characteristics of the BTV assembly mechanism reconcile previous contradictory co-assembly and core-filling models and provide insights into the mysterious RNA packaging and capsid assembly of Reoviridae members and beyond.

Keywords: RNA packaging; assembly intermediates; bluetongue virus; capsid assembly; cryo-EM; cryo-ET; cryo-FIB; dsRNA virus; duality model; viral replication cycle.

Publication types

Research Support, Non-U.S. Gov't
Research Support, N.I.H., Extramural

MeSH terms

Animals
Bluetongue virus* / genetics
Bluetongue virus* / metabolism
Bluetongue virus* / physiology
Capsid Proteins* / chemistry
Capsid Proteins* / genetics
Capsid Proteins* / metabolism
Capsid* / metabolism
Capsid* / ultrastructure
Cell Line
Cricetinae
Cryoelectron Microscopy*
Electron Microscope Tomography
Genome, Viral / genetics
Models, Molecular
RNA, Viral* / genetics
RNA, Viral* / metabolism
Viral Genome Packaging*
Virion / genetics
Virion / metabolism
Virion / ultrastructure
Virus Assembly

Substances

Capsid Proteins
RNA, Viral