eIF3d specialized translation requires a RACK1-driven eIF3d binding to 43S PIC in proliferating SH-SY5Y neuroblastoma cells

Translation initiation of most mammalian mRNAs is mediated by a 5 ' cap structure that binds eukaryotic initiation factor 4E (eIF4E). Notably, most mRNAs are still capped when eIF4E is inhibited, suggesting alternative mechanisms likely mediate cap-dependent mRNA translation without functional eIF4F. Here we found that, when eIF4E is inhibited, the ribosomal scaffold RACK1 recruits eIF3d on the 43S pre-initiation complex. Moreover, we found that it is just PKCBII in its active form that promotes the binding of RACK1 to eIF3d. These studies disclose a previously unknown role of ribosomal RACK1 for eIF3d specialized translation.