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). CPC. Does not appear to exhibit anti-apoptotic activity. 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. Expressed maternally. Expressed in the earliest stages of oocytes, and accumulates during oogenesis. Also present in early embryos with expression declining rapidly after the onset of zygotic transcription at the mid-blastula transition (MBT). Although PubMed:12454937 conclude that, with the exception of the ovary, expression is absent in adults, PubMed:16759290 suggest that expression is adult-specific and is absent in embryonic and tadpole stages between gastrulation and metamorphosis. C-terminus is required for spindle assembly. Ubiquitination is required for centrosome-targeting. Belongs to the IAP family. Extended N-terminus.