Interface between 40S exit channel protein uS7/Rps5 and eIF2? modulates start codon recognition in vivo.

ABSTRACT: The eukaryotic pre-initiation complex (PIC) bearing the eIF2·GTP·Met-tRNAiMet ternary complex (TC) scans the mRNA for an AUG codon in favorable context. AUG recognition evokes rearrangement of the PIC from an open, scanning to a closed, arrested conformation. Cryo-EM reconstructions of yeast PICs suggest remodeling of the interface between 40S protein Rps5/uS7 and eIF2? between open and closed states; however, its importance was unknown. uS7 substitutions disrupting eIF2? contacts favored in the open complex increase initiation at suboptimal sites, and uS7-S223D stabilizes TC binding to PICs reconstituted with a UUG start codon, indicating inappropriate rearrangement to the closed state. Conversely, uS7-D215 substitutions, perturbing uS7-eIF2? interaction in the closed state, confer the opposite phenotypes of hyperaccuracy and (for D215L) accelerated TC dissociation from reconstituted PICs. Thus, remodeling of the uS7/eIF2? interface appears to stabilize first the open, and then the closed state of the PIC to promote accurate AUG selection in vivo.

SUBMITTER: Visweswaraiah J 

PROVIDER: S-EPMC5323038 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature