Interaction of translation initiation factor eIF4G with eIF4A in the yeastSaccharomyces cerevisiae

Eukaryotic initiation factor (eIF) 4A is an essential protein that, in conj unction with eIF4B, catalyzes the ATP-dependent melting of RNA secondary st ructure in the 5'-untranslated region of mRNA during translation initiation , In higher eukaryotes, eIF4A is assumed to be recruited to the mRNA throug h its interaction with eIF4G, However, the failure to detect this interacti on in yeast brought into question the generality of this model, The work pr esented here demonstrates that yeast eIF4G; interacts with eIF4A both in vi vo and in vitro, The eIF4A-binding site was mapped to amino acids 542-883 o f yeast eIF4G1. Expression in yeast cells of the eIF4G1 domain that binds e IF4A results in cell growth inhibition, and addition of this domain to an e IF4A-dependent in vitro system inhibits translation in a dose-dependent man ner, Both in vitro translation and cell growth can be specifically restored by increasing the eIF4G. concentration, These data demonstrate that yeast eIF4A and eIF4G interact and suggest that this interaction is required for translation and cell growth.