Recent studies have focused attention on the role of dendritic protein synthesis in synaptic plasticity. Accordingly, a top priority of current research in this field is to identify the molecular machinery involved in processing dendritic RNAs. In preliminary studies, we have obtained evidence indicating that Translin and its partner protein, Trax, form a dendritic RNA binding complex. Therefore, we are pursuing studies aimed at defining the role of this complex in dendritic RNA processing. In previous studies conducted on brain homogenates, our laboratory identified Translin, and its partner protein, Trax, as components of a gel-shift complex capable of binding RNA or single-stranded DNA in vitro. Although these initial in vitro studies did not clarify whether the Translin/Trax complex targets RNA or DNA in vivo, two recent findings provide strong support for the view that it functions as an RNA binding complex in vivo. First, in immunohistochemical studies conducted in rat brain sections, we have found intense Translin staining in neuronal cell bodies that extends into both proximal and distal dendritic processes. The prominent somatodendritic localization of Translin strongly favors a role in RNA, rather that DNA, processing. Second, we have found that the reason why we were unable to detect the Translin/Trax complex in gel shift studies conducted on certain peripheral tissues, such as kidney, is that in kidney the complex is already occupied by endogenous RNA. Thus, the studies of the Translin/Trax complex in kidney provide compelling evidence that this complex targets RNA in vivo, while the immunohistochemical studies place Translin in neuronal dendrites. Taken together, these findings suggest that the Translin/Trax complex participates in dendritic RNA processing. To pursue these findings, we plan to conduct studies aimed at: 1) defining the localization of Trax in brain neurons, 2) identifying RNA species bound to the Translin/Trax complex in kidney, and 3) screen a panel on dendritic RNAs to identify candidate targets that bind to the Translin/Trax complex in vitro.
