Binding to the Ribosome by Eukaryotic Initiation Factor 4B Drives Yeast Translational Control in Response to Urea

The yeast eukaryotic initiation factor 4B binds the 40S subunit in translation preinitiation complexes (PICs) and promotes mRNA binding. Here we have compared the effects of disrupting eIF4B RNA- and ribosome-binding domains under ~1400 growth conditions. The RNA-binding RRM was dispensable for stress responses, but ribosome binding stimulated by the NTD promoted growth in response to a number of stressors through changes in translation. In particular, the NTD confers a strong growth advantage in the presence of the denaturing reagent, urea, and a number of osmolytes that require robust cellular integrity for survival. Ribosome profiling of cells with and without the NTD of eIF4B reveals changes in translation of mRNAs containing longer than average and highly structured 5-prime untranslated regions both normally, and in response to urea exposure. Because these changes require 40S binding, our results suggest eIF4B regulates mRNA recruitment as a part of the scanning PIC, rather than by activating isolated mRNPs prior to ribosome binding. This analysis indicates the cellular response to urea in yeast includes a translational component, driven by increased translation of mRNAs encoding proteins associated with the cellular periphery, and highlights the importance of the general translation factor eIF4B in adapting to external conditions. Two biological replicates of each Saccharomyces culture of WT without urea, mutant without urea, WT with urea, and mutant with urea were harvested. Riboseq and RNAseq libraries were derived from each set of cells for a total of 16 libraries for illumina sequencing.