title: Two RNA-binding motifs in eIF3 direct HCV IRES-dependent translation.
abstract: The initiation of protein synthesis plays an essential regulatory role in human biology. At the center of the initiation pathway, the 13-subunit eukaryotic translation initiation factor 3 (eIF3) controls access of other initiation factors and mRNA to the ribosome by unknown mechanisms. Using electron microscopy (EM), bioinformatics and biochemical experiments, we identify two highly conserved RNA-binding motifs in eIF3 that direct translation initiation from the hepatitis C virus internal ribosome entry site (HCV IRES) RNA. Mutations in the RNA-binding motif of subunit eIF3a weaken eIF3 binding to the HCV IRES and the 40S ribosomal subunit, thereby suppressing eIF2-dependent recognition of the start codon. Mutations in the eIF3c RNA-binding motif also reduce 40S ribosomal subunit binding to eIF3, and inhibit eIF5B-dependent steps downstream of start codon recognition. These results provide the first connection between the structure of the central translation initiation factor eIF3 and recognition of the HCV genomic RNA start codon, molecular interactions that likely extend to the human transcriptome.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA, Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA, Howard Hughes Medical Institute, University of California, Berkeley, CA 94720, USA, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA and Department of Chemistry, University of California, Berkeley, CA 94720, USA.
authors.forename: Chaomin
authors.initials: C
authors.lastname: Sun
authors.forename: Jordi
authors.initials: J
authors.lastname: Querol-Audí
authors.forename: Stefanie A
authors.initials: SA
authors.lastname: Mortimer
authors.forename: Ernesto
authors.initials: E
authors.lastname: Arias-Palomo
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Doudna
authors.forename: Eva
authors.initials: E
authors.lastname: Nogales
authors.forename: Jamie H D
authors.initials: JH
authors.lastname: Cate
mesh_terms: D001665:Binding Sites; D018387:Codon, Initiator / Q000235:genetics / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3 / Q000235:genetics / Q000378:metabolism*; D018257:Helix-Loop-Helix Motifs; D016174:Hepacivirus / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D011485:Protein Binding; D014176:Protein Biosynthesis; D025941:Protein Interaction Mapping; D012367:RNA, Viral / Q000235:genetics / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000235:genetics / Q000378:metabolism; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism
chemical_list: D018387:Codon, Initiator; C105988:EIF3A protein, human; D039621:Eukaryotic Initiation Factor-3; D046912:Multiprotein Complexes; D012367:RNA, Viral