Accelerates programmed cell death. Binding to the apoptosis repressors Bcl-X(L), BHRF1 or Bcl-2 suppresses this death-promoting activity. Interacts with RHBDL4/RHBDD1 (By similarity). Interacts with BCL2L10/BCL-B (By similarity). Around the nuclear envelope, and in cytoplasmic membranes. Expressed in testis, kidney, liver, lung and heart. Intact BH3 motif is required by BIK, BID, BAK, BAD and BAX for their pro-apoptotic activity and for their interaction with anti-apoptotic members of the Bcl-2 family. Proteolytically cleaved by RHBDL4/RHBDD1. RHBDL4/RHBDD1-induced cleavage is a necessary step prior its degradation by the proteosome-dependent mechanism (By similarity).