Combinations of DEAD box proteins distinguish distinct types of RNA: protein complexes in neurons.

Transport of mRNAs to axons and dendrites in neurons is important for growth, polarization and plasticity. Recent proteomic studies in neurons have identified a number of DEAD box proteins as components of RNA granules. Using DEAD box proteins as markers, we have defined classes of RNA:protein structures present in neurons. In particular, we demonstrate that the conjunction of DEAD box 1 and DEAD box 3 identifies a motile ribosome-containing RNA granule present in both axons and dendrites that is similar to the biochemically isolated RNA granule. Conjunction of DEAD box 1 and the novel protein CGI-99 defines a distinct complex in neurons. Attempts to define a P-body like structure with expression of DEAD box 6 and decapping enzymes suggest that this structure may be more complex in neuronal processes than in other compartments. These studies hint at a great complexity in RNA transport and storage in neuronal processes.