Multidomain architecture of estrogen receptor reveals interfacial cross-talk between its DNA-binding and ligand-binding domains

Human estrogen receptor alpha (hER alpha) is a hormone-responsive nuclear receptor (NR) involved in cell growth and survival that contains both a DNA-binding domain (DBD) and a ligand-binding domain (LBD). Functionally relevant inter-domain interactions between the DBD and LBD have been observed in several other NRs, but for hERa, the detailed structural architecture of the complex is unknown. By utilizing integrated complementary techniques of small-angle X-ray scattering, hydroxyl radical protein footprinting and computational modeling, here we report an asymmetric L-shaped boot structure of the multidomain hER alpha and identify the specific sites on each domain at the domain interface involved in DBD-LBD interactions. We demonstrate the functional role of the proposed DBD-LBD domain interface through site-specific mutagenesis altering the hER alpha interfacial structure and allosteric signaling. The L-shaped structure of hER alpha is a distinctive DBD-LBD organization of NR complexes and more importantly, reveals a signaling mechanism mediated by inter-domain crosstalk that regulates this receptor's allosteric function.