Multi-functional protein which regulates not only caspases and apoptosis, but also modulates inflammatory signaling and immunity, mitogenic kinase signaling and cell proliferation, as well as cell invasion and metastasis. Acts as an E3 ubiquitin-protein ligase regulating NF-kappa-B signaling and regulates both canonical and non-canonical NF-kappa-B signaling by acting in opposite directions: acts as a positive regulator of the canonical pathway and suppresses constitutive activation of non-canonical NF-kappa-B signaling. The target proteins for its E3 ubiquitin-protein ligase activity include: RIPK1, RIPK2, RIPK3, RIPK4, CASP3, CASP7, CASP8, IKBKE, TRAF1, and BCL10. Acts as an important regulator of innate immune signaling via regulation of Toll-like receptors (TLRs), Nodlike receptors (NLRs) and RIG-I like receptors (RLRs), collectively referred to as pattern recognition receptors (PRRs). Protects cells from spontaneous formation of the ripoptosome, a large multi-protein complex that has the capability to kill cancer cells in a caspase-dependent and caspase-independent manner. Suppresses ripoptosome formation by ubiquitinating RIPK1 and CASP8. S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. USP19 regulates the stability of BIRC3/c-IAP2 by preventing its ubiquitination. Interacts with PRSS25; interaction inhibits apoptotic suppressor activity. The BIR motifs region interacts with TNF receptor associated factors 1 and 2 (TRAF1 and TRAF2) to form a heteromeric complex, which is then recruited to the tumor necrosis factor receptor 2 (TNFR2). Interaction with TRAF2 is required for ubiquitination of IKBKE, degradation of NFKBIA and activation of NF-kappa-B. Interacts with RIP1, RIP2, RIP3, RIP4 and USP19. Highly expressed in fetal lung, and kidney. In the adult, expression is mainly seen in lymphoid tissues, including spleen, thymus and peripheral blood lymphocytes. Auto-ubiquitinated and degraded by the proteasome in apoptotic cells. A chromosomal aberration involving BIRC3 is recurrent in low-grade mucosa-associated lymphoid tissue (MALT lymphoma). Translocation t(11;18)(q21;q21) with MALT1. This translocation is found in approximately 50% of cytogenetically abnormal low-grade MALT lymphoma. Belongs to the IAP family.