Abstract

Yeast eIF4G1 interacts with RNA binding proteins (RBPs) like Pab1 and Pub1 affecting its function in translation initiation and stress granules formation. We present an NMR and SAXS study of the intrinsically disordered region of eIF4G1, eIF4G11-249, and its interactions with Pub1 and Pab1. The conformational ensemble of eIF4G11-249 shows an -helix within the BOX3 conserved element and a dynamic network of fuzzy {pi}-{pi} and {pi}-cation interactions involving arginine and aromatic residues. The Pab1 RRM2 domain interacts with eIF4G1 BOX3, the canonical interaction site, but also with BOX2, a conserved element of unknown function to date. In contrast, the Pub1 RRM3 domain interacts with the RNA1-1 and BOX1 regions of eIF4G1. Mixtures of Pub1, Pab1 and eIF4G1 form micrometer-size protein condensates that require the presence of the eIF4G1 BOX1 element. These homotypic interactions suggest a double key mechanism of eIF4G1 regulation, important for understanding the architecture of stress granule cores.