Component of the chromosomal passenger complex (CPC), a complex that acts as a key regulator of mitosis. The CPC complex has essential functions at the centromere in ensuring correct chromosome alignment and segregation and is required for chromatin-induced microtubule stabilization and spindle assembly. Stimulates the mitotic kinase activity of aurkb/aurora-B in the CPC. Does not appear to exhibit anti-apoptotic activity (By similarity). Component of the CPC at least composed of survivin/birc5, incenp, cdca8/borealin and/or cdca9/dasra-A, and aurkb/aurora-B. Interacts directly with incenp (via N-terminus), and may weakly interact with aurkb (via N-terminus) to stabilize the complex. Interacts with GTP-bound ran in both the S and M phases of the cell cycle. Also found in a complex with ubiquitin-mediated signaling proteins including at least usp9x/xFAM, nploc4/npl4 and ufd1 (By similarity). Localizes on chromosome arms and inner centromeres from prophase through metaphase and then transferring to the spindle midzone and midbody from anaphase through cytokinesis. C-terminus is required for spindle assembly. Ubiquitination is required for centrosome-targeting. Belongs to the IAP family.