Retards apoptosis induced by IL-3 deprivation. May function in the response of hemopoietic cells to external signals and in maintaining endothelial survival during infection (By similarity). Can inhibit apoptosis induced by serum starvation in the mammary epithelial cell line HC11 (By similarity). Interacts directly with BAK1, BID, BMF and BBC3 (By similarity). Interacts directly with BCL2L11/BIM. Interacts with BAX isoform Sigma. Interacts directly with PMAIP1. Interacts with RTL10/BOP. Interacts with ING4 (By similarity). Interacts with UBQLN4 (PubMed:34245648). Seems to be restricted to the hematopoietic compartment. Expressed in peripheral blood, spleen, and bone marrow, at moderate levels in lung, small intestine and testis, at a minimal levels in other tissues. Also found in vascular smooth muscle cells and hematopoietic malignancies. By phorbol ester and inflammatory cytokines, such as TNF or IL1B/interleukin-1 beta, but not by growth factors. Belongs to the Bcl-2 family.