Cryo-electron tomography reveals novel features of a viral RNA replication compartment
Kenneth J Ertel,
Desirée Benefield,
Daniel Castaño-Diez,
Janice G Pennington,
Mark Horswill,
Johan A den Boon,
Marisa S Otegui,
Paul Ahlquist
Affiliations
Kenneth J Ertel
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
Desirée Benefield
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Morgridge Institute for Research, University of Wisconsin-Madison, Madison, United States
Daniel Castaño-Diez
BioEM lab, Biozentrum, University of Basel, Basel, Switzerland
Janice G Pennington
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States
Mark Horswill
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Morgridge Institute for Research, University of Wisconsin-Madison, Madison, United States
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Morgridge Institute for Research, University of Wisconsin-Madison, Madison, United States
Marisa S Otegui
Department of Botany, University of Wisconsin-Madison, Madison, United States; Laboratory of Cell and Molecular Biology, University of Wisconsin-Madison, Madison, United States
Institute for Molecular Virology, University of Wisconsin-Madison, Madison, United States; Howard Hughes Medical Institute, University of Wisconsin-Madison, Madison, United States; Morgridge Institute for Research, University of Wisconsin-Madison, Madison, United States
Positive-strand RNA viruses, the largest genetic class of viruses, include numerous important pathogens such as Zika virus. These viruses replicate their RNA genomes in novel, membrane-bounded mini-organelles, but the organization of viral proteins and RNAs in these compartments has been largely unknown. We used cryo-electron tomography to reveal many previously unrecognized features of Flock house nodavirus (FHV) RNA replication compartments. These spherular invaginations of outer mitochondrial membranes are packed with electron-dense RNA fibrils and their volumes are closely correlated with RNA replication template length. Each spherule’s necked aperture is crowned by a striking cupped ring structure containing multifunctional FHV RNA replication protein A. Subtomogram averaging of these crowns revealed twelve-fold symmetry, concentric flanking protrusions, and a central electron density. Many crowns were associated with long cytoplasmic fibrils, likely to be exported progeny RNA. These results provide new mechanistic insights into positive-strand RNA virus replication compartment structure, assembly, function and control.
