title: Initiation of translation by cricket paralysis virus IRES requires its translocation in the ribosome.
abstract: The cricket paralysis virus internal ribosome entry site (CrPV-IRES) is a folded structure in a viral mRNA that allows initiation of translation in the absence of any host initiation factors. By using recent advances in single-particle electron cryomicroscopy, we have solved the structure of CrPV-IRES bound to the ribosome of the yeast Kluyveromyces lactis in both the canonical and rotated states at overall resolutions of 3.7 and 3.8 Å, respectively. In both states, the pseudoknot PKI of the CrPV-IRES mimics a tRNA/mRNA interaction in the decoding center of the A site of the 40S ribosomal subunit. The structure and accompanying factor-binding data show that CrPV-IRES binding mimics a pretranslocation rather than initiation state of the ribosome. Translocation of the IRES by elongation factor 2 (eEF2) is required to bring the first codon of the mRNA into the A site and to allow the start of translation.
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Israel S
authors.initials: IS
authors.lastname: Fernández
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Xiao-Chen
authors.initials: XC
authors.lastname: Bai
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Garib
authors.initials: G
authors.lastname: Murshudov
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
authors.forename: Sjors H W
authors.initials: SH
authors.lastname: Scheres
authors.affiliation: MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK. Electronic address: ramak@mrc-lmb.cam.ac.uk.
authors.forename: V
authors.initials: V
authors.lastname: Ramakrishnan
mesh_terms: D020285:Cryoelectron Microscopy; D056629:Dicistroviridae / Q000737:chemistry* / Q000235:genetics; D007716:Kluyveromyces / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D010442:Peptide Chain Initiation, Translational; D012333:RNA, Messenger / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012343:RNA, Transfer / Q000378:metabolism; D012367:RNA, Viral / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D012333:RNA, Messenger; D012367:RNA, Viral; D012343:RNA, Transfer