A novel eIF4E interacting protein that forms non-canonical translation initiation complexes

Translation is a fundamental step in gene expression that regulates multiple developmental and stress responses. One key step of translation initiation is the association between eIF4E and eIF4G. This process is regulated in different eukaryotes by proteins that bind to eIF4E; however, evidence of eIF4E interacting proteins able to regulate translation is missing in plants. Here, we report the discovery of CERES, a plant eIF4E interacting protein. CERES contains an LRR domain and a canonical eIF4E binding site (4E-BS). Although the CERES/eIF4E complex does not include eIF4G, CERES forms part of cap-binding complexes, interacts with eIF4A, PABP and eIF3 and co-sediments with translation initiation complexes in vivo. Moreover, CERES promotes translation in vitro and general translation in vivo, while it modulates the translation of specific mRNAs related to light- and carbohydrate-response. These data suggest that CERES is a non-canonical translation initiation factor that modulates translation in plants.