Abstract
The eukaryotic cap-binding complex eIF4F is an essential component of the translational machinery. Recognition of the mRNA cap structure through its subunit eIF4E is a requirement for the recruitment of other translation initiation factors to the mRNA 5'-end and thereby for the attachment of the 40 S ribosomal subunit. In this study, we have investigated the mechanistic basis of the observation that eIF4E binding to the cap is enhanced in the presence of the large eIF4F subunit, eIF4G. We show that eIF4E requires access to both the mRNA 5'-cap and eIF4G to form stable complexes with short RNAs. This stabilization can be achieved using fragments of eIF4G that contain the eIF4E binding site but not the RNA recognition motifs. Full-length eIF4G is shown to induce increased eIF4E binding to cap analogues that do not contain an RNA body. Both results show that interaction of eIF4G with the mRNA is not necessary to enhance cap binding by eIF4E. Moreover, we show that the effect of binding of full-length eIF4G on the cap affinity of eIF4E can be further modulated through binding of Pab1 to eIF4G. These data are consistent with a model in which heterotropic cooperativity underlies eIF4F function.
Highlights
One of the first steps during the initiation of translation on eukaryotic mRNAs is the recruitment of a translationally competent 40 S ribosomal subunit to the mRNA 5Ј-end
Recognition of the mRNA cap structure through its subunit eIF4E is a requirement for the recruitment of other translation initiation factors to the mRNA 5-end and thereby for the attachment of the 40 S ribosomal subunit
We show that eIF4E requires access to both the mRNA 5-cap and eIF4G to form stable complexes with short RNAs
Summary
One of the first steps during the initiation of translation on eukaryotic mRNAs is the recruitment of a translationally competent 40 S ribosomal subunit to the mRNA 5Ј-end This is mediated by the cap-binding complex known as eukaryotic initiation factor eIF4F. A fluorescence study determining the affinity of eIF4E in the presence of a 17-mer peptide comprising the minimal binding motif of eIF4G found no significant change in the equilibrium binding constant with soluble cap analogues [21]. The binding of this peptide to eIF4E does not alter the crystal structure of this protein [12]. We have designed a series of experiments to investigate further the proposed coop-
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
