VP-RBP, a protein enriched in brain tissue, specifically interacts with the dendritic localizer sequence of rat vasopressin mRNA

The concept of mRNA localization suggests that this process is mediated by sequences residing in the transcript to which proteins specifically bind an d ultimately deliver the mRNA along cytoskeletal elements to specific intra cellular destinations. The mRNA encoding the vasopressin (VP) precursor pro tein is localized to the nerve cell processes both in hypothalamic magnocel lular neurons and in primary cultured neurons derived from embryonic rat su perior cervical ganglia microinjected with a corresponding eukaryotic expre ssion vector. The last 395 nucleotides of the VP mRNA encompassing part of the coding region, as well as the complete 3'-untranslated region, are suff icient to confer dendritic targeting to a normally nonlocalized reporter tr anscript. Here we report that, by employing in vitro crosslinking analyses with rat brain proteins and radiolabelled VP transcripts, an RNA-binding pr otein specifically interacts with the dendritic localizer sequence of the V P mRNA. This protein is enriched in nerve cell tissues. Peripheral tissues and various cell lines contain only low amounts of the binding activity. It therefore represents a candidate protein that may be involved in any aspec t related to subcellular VP mRNA sorting in nerve cells, including transpor t and anchoring of the mRNA and possibly its translational control.