The replication protein A function of HIN200 family protein is mediated by complementation of PAAD and HIN200 domains

Our discovery of the death domain PAAD shows not only its involvement in cell death but in other biological processes. For example, we demonstrated a DNA repair function similar to Replication Protein A for the PAAD family member IFI16 (Interferon-Inducible protein 16) which also contains two HIN-200 domains by functional complementation between both individual domains. However, it is not known if the discovered ssDNA binding function is general to the HIN200 family. Here I studied MNDA (Myeloid Nuclear Differentiation Antigen), another HIN200 family member that recognizes dsDNA using similar biochemical and biophysical approaches. Our results show that MNDA has similar but distinct DNA binding properties compared to IFI16. To further map the protein-nucleic acids interface involved in these interactions, I designed mutagenesis and chemical shift mapping experiments and show that specific amino-acids side chains of the PAAD domain are critical to ssDNA and dsDNA recognition as well as nucleic-acids stabilization.