Résumé
Local translation allows for a spatial control of gene expression. Here, we performed RNA localization screen using high-throughput smFISH and discovered mRNAs locally translated at unexpected locations, including cytoplasmic protrusions, cell edges, endosomes, Golgi, the nuclear envelope and centrosomes. Surprisingly, mRNA localization frequently required ongoing translation, indicating widespread co-translational RNA targeting. We also discovered that several mRNAs accumulated in foci distinct from P-bodies, which served as specialized translation sites, i.e. translation factories. Most interestingly, we found a conserved family of mRNAs that localize to centrosomes in both human and drosophila cells. These mRNAs localize to centrosomes at different stages of the cell cycle and some also localize to cilia in quiescent cells. Drug treatments and reporter analyses revealed that mRNA localization required translation of the nascent protein. Moreover, using ASPM and NUMA1 as models, single mRNA and polysome imaging revealed active movements of endogenous polysomes towards the centrosome at the onset of mitosis, when these mRNAs start localizing. These data identify a conserved family of centrosomal mRNAs, which localize by a novel mechanism involving active polysome transport mediated by nascent proteins.