Serine/threonine-protein kinase which mediates both meiotic and mitotic chromosome segregation. Required for histone H3 'Ser-10' phosphorylation. Phosphorylates tlk-1 and zen-4 (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with zen-4 and icp-1. Part of a complex containing at least air-2; icp-1; csc-1 and bir-1. Interacts with tlk-1 and bmk-1 (By similarity). Meiotic and mitotic chromosomes. During each division, relocates to the midbody microtubules (By similarity). Belongs to the protein kinase superfamily. Ser/Thr protein kinase family.