Functional mapping of the interaction between TDP-43 and hnRNP A2 in vivo

Nuclear factor TDP-43 has been reported to play multiple roles in transcription, pre-mRNA splicing, mRNA stability and mRNA transport. From a structural point of view, TDP-43 is a member of the hnRNP protein family whose structure includes two RRM domains flanked by the N-terminus and C-terminal regions. Like many members of this family, the C-terminal region can interact with cellular factors and thus serve to modulate its function. Previously, we have described that TDP-43 binds to several members of the hnRNP A/B family through this region. In this work, we set up a coupled minigene/siRNA cellular system that allows us to obtain in vivo data to address the functional significance of TDP-43-recruited hnRNP complex formation. Using this method, we have finely mapped the interaction between TDP-43 and the hnRNP A2 protein to the region comprised between amino acid residues 321 and 366. Our results provide novel details of protein–protein interactions in splicing regulation. In addition, we provide further insight on TDP-43 functional properties, particularly the lack of effects, as seen with our assays, of the disease-associated mutations that fall within the TDP-43 321-366 region: Q331K, M337V and G348C.