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  • The EMBO Journal (2007) 26, 1602 - 1614
  • doi:10.1038/sj.emboj.7601613

Published online: 1 March 2007

N- and C-terminal residues of eIF1A have opposing effects on the fidelity of start codon selection

Christie A Fekete1,a, Sarah F Mitchell2,a, Vera A Cherkasova1, Drew Applefield2, Mikkel A Algire2, David Maag2, Adesh K Saini1, Jon R Lorsch2 and Alan G Hinnebusch1

  1. Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, NIH, Bethesda, MD, USA
  2. Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore MD, USA

Correspondence to:

Jon R Lorsch, Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, 725 N. Wolfe St, 625 WBSB, Baltimore, MD 21205, USA. Tel.: +1 (410) 955 3012; Fax: +1 (410) 955 0637; E-mail: jlorsch@jhmi.edu

Alan G Hinnebusch, Laboratory of Gene Regulation and Development, National Institute of Child Health and Human Development, NIH, Building 6A/Room B1A-13, Bethesda, MD 20892, USA. Tel.: +1 (301) 496 4480; Fax: +1 (301) 496-6828; E-mail: ahinnebusch@nih.gov

aThese authors contributed equally to this work

Received 4 October 2006; Accepted 22 January 2007

Translation initiation factor eIF1A stimulates preinitiation complex (PIC) assembly and scanning, but the molecular mechanisms of its functions are not understood. We show that the F131A,F133A mutation in the C-terminal tail (CTT) of eIF1A impairs recruitment of the eIF2-GTP-Met-tRNAiMet ternary complex to 40S subunits, eliminating functional coupling with eIF1. Mutating residues 17–21 in the N-terminal tail (NTT) of eIF1A also reduces PIC assembly, but in a manner rescued by eIF1. Interestingly, the 131,133 CTT mutation enhances initiation at UUG codons (Sui- phenotype) and decreases leaky scanning at AUG, while the NTT mutation 17–21 suppresses the Sui- phenotypes of eIF5 and eIF2beta mutations and increases leaky scanning. These findings and the opposite effects of the mutations on eIF1A binding to reconstituted PICs suggest that the NTT mutations promote an open, scanning-conducive conformation of the PIC, whereas the CTT mutations 131,133 have the reverse effect. We conclude that tight binding of eIF1A to the PIC is an important determinant of AUG selection and is modulated in opposite directions by residues in the NTT and CTT of eIF1A.

  • Keywords:

    • eIF1A,
    • GCN4,
    • initiation,
    • Saccharomyces,
    • translation