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. Contributes to CPC function by facilitating loading of the CPC onto chromosomes (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 with incenp (via N-terminus) (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. Belongs to the borealin family.