title: Yeast eIF4B binds to the head of the 40S ribosomal subunit and promotes mRNA recruitment through its N-terminal and internal repeat domains.
abstract: Eukaryotic translation initiation factor (eIF)4B stimulates recruitment of mRNA to the 43S ribosomal pre-initiation complex (PIC). Yeast eIF4B (yeIF4B), shown previously to bind single-stranded (ss) RNA, consists of an N-terminal domain (NTD), predicted to be unstructured in solution; an RNA-recognition motif (RRM); an unusual domain comprised of seven imperfect repeats of 26 amino acids; and a C-terminal domain. Although the mechanism of yeIF4B action has remained obscure, most models have suggested central roles for its RRM and ssRNA-binding activity. We have dissected the functions of yeIF4B's domains and show that the RRM and its ssRNA-binding activity are dispensable in vitro and in vivo. Instead, our data indicate that the 7-repeats and NTD are the most critical domains, which mediate binding of yeIF4B to the head of the 40S ribosomal subunit via interaction with Rps20. This interaction induces structural changes in the ribosome's mRNA entry channel that could facilitate mRNA loading. We also show that yeIF4B strongly promotes productive interaction of eIF4A with the 43S•mRNA PIC in a manner required for efficient mRNA recruitment.
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Sarah E
authors.initials: SE
authors.lastname: Walker
authors.forename: Fujun
authors.initials: F
authors.lastname: Zhou
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Mitchell
authors.forename: Victoria S
authors.initials: VS
authors.lastname: Larson
authors.forename: Leos
authors.initials: L
authors.lastname: Valasek
authors.forename: Alan G
authors.initials: AG
authors.lastname: Hinnebusch
authors.forename: Jon R
authors.initials: JR
authors.lastname: Lorsch
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D039601:Eukaryotic Initiation Factor-4A / Q000235:genetics / Q000378:metabolism*; D039642:Eukaryotic Initiation Factors / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010442:Peptide Chain Initiation, Translational; D011132:Polyribosomes / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis; D017434:Protein Structure, Tertiary; D012331:RNA, Fungal / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism*; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism*; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017384:Sequence Deletion
chemical_list: D039642:Eukaryotic Initiation Factors; D012331:RNA, Fungal; D012333:RNA, Messenger; D012337:RNA, Ribosomal, 18S; D016601:RNA-Binding Proteins; C088045:RPS20 protein, S cerevisiae; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C031799:eIF-4B; D039601:Eukaryotic Initiation Factor-4A