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 or AURKC, 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/C toward substrates near microtubules (PubMed:15316025, PubMed:12925766, PubMed:27332895). The flexibility of the SAH domain is proposed to allow AURKB/C to follow substrates on dynamic microtubules while ensuring CPC docking to static chromatin (By similarity). Activates AURKB and AURKC (PubMed:27332895). Required for localization of CBX5 to mitotic centromeres (PubMed:21346195). Controls the kinetochore localization of BUB1 (PubMed:16760428). Component of the chromosomal passenger complex (CPC) composed of at least BIRC5/survivin, CDCA8/borealin, INCENP, AURKB or AURKC; in the complex binds directly to AURKB or AURKC via the IN box, and forms a triple-helix bundle-based subcomplex with BIRC5 and CDCA8 via its N-terminus (PubMed:17956729, PubMed:27332895). The reported homodimerization is questioned as the SAH domain is shown to be monomeric (By similarity). Interacts with H2AZ1 (By similarity). Interacts with CBX1 and CBX3. Interacts with tubulin beta chain. Interacts with EVI5. Interacts with CBX5; POGZ and INCENP compete for interaction with CBX5; regulates INCENP (and probably CPC) localization to centromeres in interphase and not required for proper mitotic progression or sister chromatid cohesion. Interacts with POGZ. Interacts with JTB. Colocalized at synaptonemal complex central element from zygotene up to late pachytene when it begins to relocalize to heterochromatic chromocenters. Colocalizes with AURKB at a connecting strand traversing the centromere region and joining sister kinetochores, in metaphase II centromeres. This strand disappears at the metaphase II/anaphase II transition and relocalizes to the spindle midzone (By similarity). Colocalizes with AURKB at mitotic chromosomes (PubMed:11453556). Localizes to inner kinetochore (PubMed:16760428). Localizes on chromosome arms and inner centromeres from prophase through metaphase and then transferring to the spindle midzone and midbody from anaphase through cytokinesis (PubMed:15316025). Cocalizes to the equatorial cell cortex at anaphase (PubMed:11453556). 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. Phosphorylation by AURKB or AURKC at its C-terminal part is important for AURKB or AURKC activation by INCENP. Belongs to the INCENP family. PubMed:11139336 experiments have been carried out partly in chicken and partly in human. Originally predicted to contain a coiled coil domain but shown to contain a stable SAH domain instead.