Dynamic Recognition of the mRNA Cap by Saccharomyces cerevisiae eIF4E

• DOI: 10.1016/j.str.2013.09.016
• Publication Date: 2013-10-31T17:33:04Z
• Authors: Seán E. O’Leary; Alexey Petrov; Jin Chen; Joseph D. Puglisi
• Keywords: EIF4G; EIF4E; eIF4A; Poly(N-isopropylacrylamide); Initiation factor

Recognition of the mRNA 5' m⁷G(5')ppp(5')N cap is key to translation initiation for most eukaryotic mRNAs. The cap is bound by the eIF4F complex, consisting of a cap-binding protein (eIF4E), a "scaffold" protein (eIF4G), and an RNA helicase (eIF4A). As a central early step in initiation, regulation of eIF4F is crucial for cellular viability. Although the structure and function of eIF4E have been defined, a dynamic mechanistic picture of its activity at the molecular level in the eIF4F·mRNA complex is still unavailable. Here, using single-molecule fluorescence, we measured the effects of Saccharomyces cerevisiae eIF4F factors, mRNA secondary structure, and the poly(A)-binding protein Pab1p on eIF4E-mRNA binding dynamics. Our data provide an integrated picture of how eIF4G and mRNA structure modulate eIF4E-mRNA interaction, and uncover an eIF4G- and poly(A)-independent activity of poly(A)-binding protein that prolongs the eIF4E·mRNA complex lifetime.