Physical interaction of HIRA, UBN1, and CABIN1. (A) Schematic alignment of CABIN1 and S. cerevisiae Hir3p showing conserved N-terminal TPRs. (B) Ectopically expressed HA-HIRA and myc-CABIN1 interaction, detected by coimmunoprecipitation (IP) with anti-HA antibodies. (C) siRNA-mediated knockdown of endogenous HIRA and CABIN1 confirms specificity of HIRA and CABIN1 antibodies. (D) siRNA-mediated knockdown of endogenous CABIN1 confirms specificity of the CABIN1 antibody by immunofluorescence. (E) Interaction of endogenous HIRA and CABIN1 in osteosarcoma cells (U2OS) and primary fibroblasts (IMR90), detected by coimmunoprecipitation with antibodies to HIRA (WC15 and D32) and CABIN1 (ab3349). Anti-mouse IgG (anti-myc 9E10; Santa Cruz) and anti-rabbit IgG (M7023; Sigma) were used as control IgGs for mouse and rabbit antibodies, respectively. (F) Interaction of endogenous UBN1 and CABIN1, detected by coimmunoprecipitation with antibodies to CABIN1 (ab3349).