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. {ECO:0000269|PubMed:15260989; ECO:0000269|PubMed:17199039}.