Ribosomes in RNA granules are stalled on mRNA sequences that are consensus sites for FMRP association

Neurons send mRNAs to synapses in RNA granules, where they are not translated until an appropriate stimulus is given. Here we characterize a granule fraction from sucrose gradients and show that polysomes in this fraction are stalled on consensus sequences in a specific state of translational arrest with extended ribosome-protected fragments. This greatly increases our understanding of how neurons use specialized mechanisms to regulate translation and suggests many studies on neuronal translation may need to be re-evaluated to include the large fraction of neuronal polysomes found in the pellet of sucrose gradients used to isolate polysomes