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Elife. 2017 Nov 30;6. pii: e31476. doi: 10.7554/eLife.31476.

Yeast eIF4A enhances recruitment of mRNAs regardless of their structural complexity.

Author information

1
Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States.
2
Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States.

Abstract

eIF4A is a DEAD-box RNA-dependent ATPase thought to unwind RNA secondary structure in the 5'-untranslated regions (UTRs) of mRNAs to promote their recruitment to the eukaryotic translation pre-initiation complex (PIC). We show that eIF4A's ATPase activity is markedly stimulated in the presence of the PIC, independently of eIF4E•eIF4G, but dependent on subunits i and g of the heteromeric eIF3 complex. Surprisingly, eIF4A accelerated the rate of recruitment of all mRNAs tested, regardless of their degree of structural complexity. Structures in the 5'-UTR and 3' of the start codon synergistically inhibit mRNA recruitment in a manner relieved by eIF4A, indicating that the factor does not act solely to melt hairpins in 5'-UTRs. Our findings that eIF4A functionally interacts with the PIC and plays important roles beyond unwinding 5'-UTR structure is consistent with a recent proposal that eIF4A modulates the conformation of the 40S ribosomal subunit to promote mRNA recruitment.

KEYWORDS:

RNA helicase; S. cerevisiae; biochemistry; biophysics; eIF4A; eIF4F; mRNA recruitment; ribosome; structural biology; translation initiation

PMID:
29192585
PMCID:
PMC5726853
DOI:
10.7554/eLife.31476
[Indexed for MEDLINE]
Free PMC Article

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