BIRC6

Anti-apoptotic protein known as inhibitor of apoptosis (IAP) which can regulate cell death by controlling caspases and by acting as an E3 ubiquitin-protein ligase. Unlike most IAPs, does not contain a RING domain and it is not a RING-type E3 ligase. Instead acts as a dual E2/E3 enzyme that combines ubiquitin conjugating (E2) and ubiquitin ligase (E3) activities in a single polypeptide. Ubiquitination is mediated by a non-canonical E1 ubiquitin activating enzyme UBA6. Ubiquitinates CASP3, CASP7 and CASP9 and inhibits their caspase activity; also ubiquitinates their procaspases but to a weaker extent. Ubiquitinates pro-apoptotic factors DIABLO/SMAC and HTRA2. DIABLO/SMAC antagonizes the caspase inhibition activity of BIRC6 by competing for the same binding sites as the caspases. Ubiquitinates the autophagy protein MAP1LC3B; this activity is also inhibited by DIABLO/SMAC. Important regulator for the final stages of cytokinesis. Crucial for normal vesicle targeting to the site of abscission, but also for the integrity of the midbody and the midbody ring, and its striking ubiquitin modification..

Function from UniProtKB (Q9NR09), read 2026-09-23. CC BY 4.0.