Mechanism of membrane perforation in rotavirus cell entry

Non-enveloped viral cell entry -- like delivery of biological therapeutics -- requires translocation of a macromolecular assembly across a membrane. Double-strand RNA viruses introduce into their target cells an inner capsid particle that does not uncoat further but instead extrudes capped viral mRNA by virtue of polymerase and capping activities within it. We have used cryogenic electron tomography to visualize the full course of rhesus rotavirus entry, from cell attachment and virion uptake to release of the subviral particle. The cryo-tomograms and subtomogram averaging of classified subparticles link high-resolution structures of the virion and its components with time series from live-cell fluorescence microscopy and thus outline the mechanism of each step in the entry process, including the hitherto elusive membrane perforation step that transfers a subviral particle into the cytosol.