In polarized cells, the translation of at least a fraction of newly made mRNAs appears to be inhibited until the mRNA is properly transported in granules to a distal projection. Where in the cell and when, if at all, during transport and localization the CBC is replaced by eIF4E remains to be determined. Based on work using non-polarized cells, FMRP binding to target mRNAs, including NMD targets, requires its direct interaction with PABPC1, which is bound to the poly(A) tail of the mRNA. According to this model, once localized to a distal projection, FMRP is removed from the NMD target by the dephosphorylation of FMRP, allowing translation and, as a consequence, decay by NMD. The step(s) at which translation is inhibited prior to granule localization remains to be defined
