Functional analysis of Drosophila eIF4E in P bodies.

FERRERO PV; LAYANA C; PAULUCCI E; RIVERA POMAR R

San Diego

Congreso; 52nd Annual Drosophila Research Conference; 2011

The eukaryotic translation initiation factor 4E isoform 1 (eIF4E-1) is the main of eitgh eIF4E isoforms that are expressed in Drosophila. It plays a major role in translation and the absence of eIF4E-1 is lethal. eIF4E-1 is present in the cytoplasm of the cells as soluble protein, in translational complexes and also in P bodies, the cytoplasmic foci involved in mRNA silencing. eIF4E is the only translation factor present in either active or inactive mRNPs. To elucidate the pathways of silencing mediated by eIF4E we have studied the interactions between eIF4E, mRNAs and PBs components in vivo. We have generated eIF4E mutants on key tryptophan (W) residues by replacing them with alanine (A). We transfected S2 cells with either wild type and mutant eIF4E-1 to evaluate the requeriment for PBs formation and localization. Mutation of W117 results in the absence of eIF4E-1 in P bodies, but it does not affect the formation of the foci. Mutations in W residues required for cap-binding did not affect the presence of eIF4E-1 in P bodies. This was also observed in cross-experiments in HeLa cells.Therefore we conclude that protein-protein interactions rather than cap-binding are required for the transition from polysomes to P bodies.