Somatodendritic localization of Translin, a component of the Translin/TraxRNA binding complex

Recent studies implicating dendritic protein synthesis in synaptic plastici ty have focused attention on identifying components of the molecular machin ery involved in processing dendritic RNA. Although Translin was originally identified as a protein capable of binding single-stranded DNA, subsequent studies have demonstrated that it also binds RNA in vitro. Because previous studies indicated that Translin-containing RNA/single-stranded DNA binding complexes are highly enriched in brain, we and others have proposed that i t may be involved in dendritic RNA processing. To assess this possibility, we have conducted studies aimed at defining the localization of Translin an d its partner protein, Trax, in brain. In situ hybridization studies demons trated that both Translin and Trax are expressed in neurons with prominent staining apparent in cerebellar Purkinje cells and neuronal layers of the h ippocampus. Subcellular fractionation studies demonstrated that both Transl in and Trax are highly enriched in the cytoplasmic fraction compared with n uclear extracts. Furthermore, immunohistochemical studies with Translin ant ibodies revealed prominent staining in Purkinje neuron cell bodies that ext ends into proximal and distal dendrites. A similar pattern of somatodendrit ic localization was observed in hippocampal and neocortical pyramidal neuro ns. These findings demonstrate that Translin is expressed in neuronal dendr ites and therefore support the hypothesis that the Translin/Trax complex ma y be involved in dendritic RNA processing.