Cryo-EM shows the polymerase structures and a nonspooled genome within a dsRNA virus
Double-stranded RNA (dsRNA) viruses possess a segmented dsRNA genome and a
number of RNA-dependent RNA polymerases (RdRps) enclosed in a capsid. Until now,
the precise structures of genomes and RdRps within the capsids have been unknown.
Here we report the structures of RdRps and associated RNAs within nontranscribing
and transcribing cypoviruses (NCPV and TCPV, respectively), using a combination of
cryo–electron microscopy (cryo-EM) and a symmetry-mismatch reconstruction method. The
RdRps and associated RNAs appear to exhibit a pseudo-D3 symmetric organization in both
NCPV and TCPV. However, the molecular interactions between RdRps and the genomic
RNA were found to differ in these states. Our work provides insight into the mechanisms
of the replication and transcription in dsRNA viruses and paves a way for structural
determination of lower-symmetry complexes enclosed in higher-symmetry structures.
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