Molecular Cell (@cp-molcell.bsky.social)

Capsid restructuring activates semi-conservative dsRNA transcription in cystovirus ɸ6 Ilca et al. uncover how the double-stranded RNA cystovirus ɸ6 activates its semi-conservative transcription inside its double-layered capsid. Using cryogenic electron microscopy and localized reconstruction, they visualize how nucleotide binding triggers shedding of the outer capsid layer, expansion of the inner layer, and assembly of a triskelion-shaped complex of the minor protein P7 at opposite poles of the spooled genome. These complexes organize the viral RNA-dependent RNA polymerases (P2) to initiate transcription, with the newly synthesized mRNA exiting through the hexameric P4 channels. The results reveal a multi-step structural transition that converts a quiescent capsid into an active transcriptional nanomachine. http://dlvr.it/TQXBjB