Yeast eIF4B binds the small ribosomal subunit and promotes mRNA recruitment during translation initiation.

Monday, September 22, 2014 — Poster Session II
4:00 p.m. – 6:00 p.m.	FAES Academic Center	NIGMS	DIR-13

* FARE Award Winner

Authors

• S.E. Walker
• F. Zhou
• S.F. Mitchell
• V.S. Larson
• A.G. Hinnebusch
• J.R. Lorsch

Abstract

Recruitment of mRNAs to the ribosomal translation preinitiation complex (PIC) in eukaryotic cells serves as a major point of regulation of gene expression. The current model for mRNA recruitment hinges on a strong role for the eukaryotic translation initiation factor (eIF)4 group of factors, which are proposed to bind the 5’ends of mRNAs and activate their translation by unwinding secondary structures. A key feature of this model is that eIF4B acts by binding to ssRNA that has been unwound by eIF4F to generate a single-stranded ribosomal landing pad. Here we demonstrate that eIF4B instead binds directly to a protein in the 40S ribosomal subunit to promote eIF4F activity and mRNA binding. Upon binding, eIF4B induces structural changes in the mRNA entry channel of the 40S. Disruption of eIF4B elements required for 40S binding, but not disruption of the RNA recognition motif and associated ssRNA-binding activities, abrogates the ability of eIF4B to stimulate mRNA recruitment and eIF4F function in vitro and in vivo. These results support a model in which yeast eIF4B binds the ribosome in a manner that promotes eIF4A function and a receptive state of the mRNA binding channel, rather than by acting as a ssRNA-binding protein.

back to top