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. Can inhibit apoptosis induced by serum starvation in the mammary epithelial cell line HC11 (PubMed:11888890). Interacts directly with BCL2L11/BIM and PMAIP1 (By similarity). Interacts directly with BAK1, BID, BMF and BBC3. Interacts with BOP (By similarity). Interacts with isoform 3, isoform 4 and isoform 5 of ING4. Interacts with UBQLN4 (By similarity). Expressed in hemopoietic tissues, including bone marrow, spleen and thymus. By granulocyte-macrophage colony-stimulating factor and LPS in macrophages. Belongs to the Bcl-2 family.