Structure of mammalian eIF3 in the context of the 43S preinitiation complex.
During eukaryotic translation initiation, 43S complexes, comprising a 40S ribosomal subunit, initiator transfer RNA and initiation factors (eIF) 2, 3, 1 and 1A, attach to the 5'-terminal region of messenger RNA and scan along it to the initiation codon. Scanning on structured mRNAs also requires the DExH-box protein DHX29. Mammalian eIF3 contains 13 subunits and participates in nearly all steps of translation initiation. Eight subunits having PCI (proteasome, COP9 signalosome, eIF3) or MPN (Mpr1, Pad1, amino-terminal) domains constitute the structural core of eIF3, to which five peripheral subunits are flexibly linked. Here we present a cryo-electron microscopy structure of eIF3 in the context of the DHX29-bound 43S complex, showing the PCI/MPN core at ∼6 Å resolution. It reveals the organization of the individual subunits and their interactions with components of the 43S complex. We were able to build near-complete polyalanine-level models of the eIF3 PCI/MPN core and of two peripheral subunits. The implications for understanding mRNA ribosomal attachment and scanning are discussed.
HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.
Amedee
A
des Georges
Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
Vidya
V
Dhote
CNRS, Proteomic Platform Strasbourg - Esplanade, Strasbourg 67084, France.
Lauriane
L
Kuhn
Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
Christopher U T
CU
Hellen
Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
Tatyana V
TV
Pestova
HHMI, Department of Biochemistry and Molecular Biophysics, Columbia University, New York, New York 10032, USA.|Department of Biological Sciences, Columbia University, New York, New York 10032, USA.
Joachim
J
Frank
CNRS, Architecture et Réactivité de l'ARN, Université de Strasbourg, Strasbourg 67084, France.
Yaser
Y
Hashem
D001665:Binding Sites; D018387:Codon, Initiator / Q000235:genetics; D020285:Cryoelectron Microscopy; D015852:Eukaryotic Initiation Factor-2 / Q000737:chemistry / Q000378:metabolism; D039621:Eukaryotic Initiation Factor-3 / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000378:metabolism*; D010442:Peptide Chain Initiation, Translational; D010448:Peptide Initiation Factors / Q000378:metabolism; D017433:Protein Structure, Secondary; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D020365:RNA Helicases / Q000737:chemistry / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012358:RNA, Transfer, Met / Q000378:metabolism; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry / Q000378:metabolism; D012270:Ribosomes / Q000737:chemistry* / Q000378:metabolism*
D018387:Codon, Initiator; D015852:Eukaryotic Initiation Factor-2; D039621:Eukaryotic Initiation Factor-3; D046912:Multiprotein Complexes; D010448:Peptide Initiation Factors; D021122:Protein Subunits; D012333:RNA, Messenger; D012358:RNA, Transfer, Met; C534219:DHX29 protein, human; D020365:RNA Helicases