The entry represents the UBA domain found in c-IAPs, including BIRC2 (also known as C-IAP1) and BIRC3 (also known as C-IAP2). c-IAPs function as ubiquitin E3 ligases that mediate the ubiquitination of the substrates involved in apoptosis, nuclear factor-kappaB (NF-kappaB) signaling, and oncogenesis [, ]. Unlike other apoptosis proteins such as XIAP, c-IAPs exhibit minimal binding to caspases and may not play an important role in the inhibition of these proteases. c-IAP1 is a potent regulator of the tumor necrosis factor (TNF) receptor family and NF-kappaB signaling pathways in the cytoplasm. It can also regulate E2F1 transcription factor-mediated control of cyclin transcription in the nucleus []. c-IAP2 also influences ubiquitin-dependent pathways that modulate innate immune signalling by activation of NF-kappaB []. c-IAPs contain three N-terminal baculoviral IAP repeat (BIR) domains that enable interactions with proteins, a ubiquitin-association (UBA) domain that is responsible for the binding of polyubiquitin (polyUb), a caspase activation and recruitment domain (CARD) that serves as a protein interaction surface, and a RING domain at the carboxyl terminus that is required for ubiquitin ligase activity [, ].
