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. Acts as a scaffold regulating CPC localization and activity. The C-terminus associates with AURKB, the N-terminus associated with BIRC5/survivin and CDCA8/borealin tethers the CPC to the inner centromere, and the microtubule binding activity within the central SAH domain directs AURKB toward substrates near microtubules. The flexibility of the SAH domain is proposed to allow AURKB to follow substrates on dynamic microtubules while ensuring CPC docking to static chromatin. Activates AURKB. Component of the chromosomal passenger complex (CPC) composed of at least BIRC5/survivin, CDCA8/borealin, INCENP and AURKB; in the complex binds directly to AURKB via the IN box, and forms a triple-helix bundle-based subcomplex with BIRC5 and CDCA8 via its N-terminus. The initially reported homodimerization is questioned as the SAH domain is shown to be monomeric. Interacts with CBX5. Is restricted to the nucleus in interphase, remains tightly bound to the chromosomes until early metaphase, and during late metaphase gets concentrated in linear arrays that transect the metaphase plate between the chromosomes (PubMed:8408220). As anaphase begins to move to the spindle midzone where it is intimately associated with the bundled microtubules (PubMed:8408220). Later in anaphase gets closely associated with the cell cortex, and by telophase is concentrated at each side of the midbody in the intercellular bridge, with which it is discarded after (PubMed:8408220). The IN box mediates interaction with AURKB and AURKC. The SAH (single alpha-helix) region is characterized by a high content of charged residues which are predicted to stabilize the alpha-helical structure by ionic bonds. It can refold after extension suggesting an in vivo force-dependent function. The isolated SAH domain is monomeric. Belongs to the INCENP family. Originally predicted to contain a coiled coil domain but shown to contain a stable SAH domain instead.