Cryo-EM of ribosomal 80S complexes with termination factors reveals the translocated cricket paralysis virus IRES.

ABSTRACT: The cricket paralysis virus (CrPV) uses an internal ribosomal entry site (IRES) to hijack the ribosome. In a remarkable RNA-based mechanism involving neither initiation factor nor initiator tRNA, the CrPV IRES jumpstarts translation in the elongation phase from the ribosomal A site. Here, we present cryoelectron microscopy (cryo-EM) maps of 80S?CrPV-STOP ? eRF1 ? eRF3 ? GMPPNP and 80S?CrPV-STOP ? eRF1 complexes, revealing a previously unseen binding state of the IRES and directly rationalizing that an eEF2-dependent translocation of the IRES is required to allow the first A-site occupation. During this unusual translocation event, the IRES undergoes a pronounced conformational change to a more stretched conformation. At the same time, our structural analysis provides information about the binding modes of eRF1 ? eRF3 ? GMPPNP and eRF1 in a minimal system. It shows that neither eRF3 nor ABCE1 are required for the active conformation of eRF1 at the intersection between eukaryotic termination and recycling.

SUBMITTER: Muhs M 

PROVIDER: S-EPMC4526138 | biostudies-literature | 2015 Feb

REPOSITORIES: biostudies-literature