Hu proteins are RNA-binding proteins that are implicated in the control of 
stabilization, nuclear export, and/or translation of specific mRNAs with AU-rich 
elements (AREs) in the 3'-untranslated region. Three neuron-specific Hu proteins 
(HuD, HuB, and HuC), but not a ubiquitously expressed Hu protein HuR, have an 
activity to induce neurite outgrowth when they are overexpressed in a rat 
neuronal cell line PC12. Here we show that TAP/NXF1, the primary export receptor 
for the bulk mRNA, is a specific binding partner for HuD. In vitro binding 
experiments using recombinant proteins revealed that the interaction between TAP 
and HuD is direct and that HuD can form a ternary complex together with both TAP 
and RNA. Interestingly, HuR does not interact with TAP. These results suggest 
that HuD acts as a novel adaptor protein to recruit TAP for efficient export of 
ARE-containing mRNAs in neuronal cells.