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Structure of eukaryotic initiation factors at interfaces within ribosomal preinitiation complexes: Yeast perspectives
Author(s) -
Asano Katsura,
Singh C Ranjit,
Reibarkh Mikhail,
Yamamoto Yasufumi,
Marintchev Assen,
Lee Bumjun,
Del Rio Federico,
Wagner Gerhard
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a502-c
Subject(s) - eif4g , transcription preinitiation complex , eukaryotic small ribosomal subunit , initiation factor , biology , eukaryotic translation , eukaryotic initiation factor , microbiology and biotechnology , eif2 , genetics , translation (biology) , messenger rna , gene expression , promoter , gene
In eukaryotic translation, initiation factors (eIFs) promote delivery of Met‐tRNA i Met and 5′‐capped mRNA to the 40S subunit to form 43S and 48S preinitiation complexes, respectively. In yeast, eIF1A and a multifactor complex (MFC) containing eIF1, eIF2, eIF3, eIF5, and Met‐tRNA i Met bind to the 40S subunit to form the 43S complex. Interaction of eIF4G with eIF1 and eIF5 promotes the 48S complex formation. The eIF5‐C‐terminal domain (CTD) and eIF1 are crucial core elements for the preinitiation complex assembly. Here we determine by NMR spectroscopy the solution structure of yeast eIF1 and identify its interfaces to eIF5‐CTD at its acidic N‐terminal tail (NTT) and a basic surface. Mutational studies on eIF1 confirm the eIF5‐CTD‐binding sites and show that the basic surface also serves as the eIF4G‐binding site. We also identify a distinct eIF3c‐binding site on eIF1 and the binding site for eIF2β, eIF1, eIF3 and eIF4G on the homology modeled structure of eIF5‐CTD. Mutation in the predicted eIF4G‐binding site of eIF1 is lethal. Mutations in the eIF1‐NTT and the eIF5‐surface areas are not lethal but impair GCN4 translational control by disrupting preinitiation complex interactions. Based on these and other results, we propose that eIF2β and eIF3c together form a clamp to embrace the eIF5‐CTD/eIF1 complex for MFC assembly, which sequesters eIF1 until it binds eIF4G and the ribosomal P‐site in the preinitiation complex function. Supported by NIH RO1 GM64781 to KA and CA68262 to GW.