Domain architecture of Sir4. Crystal structures have been determined for the Sir4 Ku80-binding motif (KBM) in complex with Ku80, the Sir4-interacting domain (SID) in complex with Sir2, and the Sir4 self-dimerization coiled-coil module (CC) (PDB 5Y59, 4IAO, and 1NYH, respectively). Sir4 H‑BRCT (orange box, this work) locates to the first half of the partitioning and anchoring domain (PAD) which recruits silenced chromatin to the nuclear envelope. 