Mechanism for Coordinated RNA Packaging and Genome Replication by Rotavirus Polymerase VP1

SummaryRotavirus RNA-dependent RNA polymerase VP1 catalyzes RNA synthesis within a subviral particle. This activity depends on core shell protein VP2. A conserved sequence at the 3′ end of plus-strand RNA templates is important for polymerase association and genome replication. We have determined the structure of VP1 at 2.9 Å resolution, as apoenzyme and in complex with RNA. The cage-like enzyme is similar to reovirus λ3, with four tunnels leading to or from a central, catalytic cavity. A distinguishing characteristic of VP1 is specific recognition, by conserved features of the template-entry channel, of four bases, UGUG, in the conserved 3′ sequence. Well-defined interactions with these bases position the RNA so that its 3′ end overshoots the initiating register, producing a stable but catalytically inactive complex. We propose that specific 3′ end recognition selects rotavirus RNA for packaging and that VP2 activates the autoinhibited VP1/RNA complex to coordinate packaging and genome replication.