Serine/threonine-protein kinase component of the chromosomal passenger complex (CPC), a complex that acts as a key regulator of chromosome segregation and cytokinesis (PubMed:12707312, PubMed:11050385, PubMed:10983970, PubMed:9852156, PubMed:10354474, PubMed:10975519, PubMed:11050384). The CPC complex has essential functions at the centromere in ensuring correct chromosome alignment and segregation (PubMed:12707312, PubMed:10983970). Required for histone H3 phosphorylation during segregation of homologous chromosomes in meiosis and mitosis (PubMed:18923084). Required for histone H3 'Ser-10' phosphorylation (PubMed:9852156, PubMed:10354474, PubMed:10975519, PubMed:11050384, PubMed:11050385, PubMed:10983970, PubMed:12015116, PubMed:11940606). Phosphorylates tlk-1 at 'Ser-634', which enhances its activity (PubMed:15916946). Phosphorylates zen-4 at 'Ser-680'(PubMed:15854913). Required for the recruitment of bub-1 to the ring-shaped domain between chromosomes during meiotic anaphase I (PubMed:20729837). Also required for the localization of the condensin I complex subunit smc-4 to mitotic chromosomes (PubMed:11914278). Acts at the spindle midzone and the midbody to prevent cleavage furrow regression upon chromatin obstructions during cytokinesis (PubMed:12213836, PubMed:23684975). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Component of the CPC complex which consists of icp-1; csc-1; bir-1 and air-2 (PubMed:12707312). Within the complex, interacts with icp-1; csc-1 and bir-1 (PubMed:12707312, PubMed:11050385). Interacts with zen-4 (PubMed:11050384). Interacts with tlk-1 and bmk-1 (PubMed:15548597, PubMed:15916946). Meiotic and mitotic chromosomes (PubMed:9852156, PubMed:18923084). During each division, relocates to the midbody microtubules (PubMed:9852156, PubMed:23684975). Localizes on chromosomes during metaphase and on the central spindle during anaphase (PubMed:25475837, PubMed:23684975). Localization to homologous chromosomes during segregation is dependent on lab-1 (PubMed:18923084). Present during gametogenesis and throughout embryogenesis (at protein level). Phosphorylated. Increased phosphorylation upon chromatin obstructions at anaphase. RNAi-mediated knockdown disrupts the localization of the condensin subunit smc-4 to mitotic chromosomes (PubMed:11914278). RNAi-mediated knockdown causes failure in mitotic chromosome segregation and cytokinesis, leading to aneuploidy (PubMed:11914278, PubMed:12213836). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family. Aurora subfamily.