CDK1 (CDC2) in complex with CCNB (cyclin B) phosphorylates condensin I subunits NCAPD2, NCAPG and NCAPH in mitosis (Kimura et al. 2001, Takemoto et al. 2006), but other mitotic kinases may also be involved. CDK1 phosphorylation sites in NCAPH have not been established. NCAPD2 threonine residues T1339, T1384 and T1389 are inferred to be phosphorylated by CDK1 based on homologues sites in Xenopus laevis Ncapd2 (Kimura et al. 1998). NCAPG threonine residues T308 and T332 are phosphorylated by CDK1 in vitro and functionally important. The functional importance of threonine T931, also phosphorylated by CDK1 in vitro, has not been demonstrated (Murphy et al. 2008). Phosphorylation by CDK1 is required for mitotic activation of condensin I and promotes chromosomal binding, introduction of positive supercoils into DNA, and chromatin condensation (Kimura et al. 1998, Kimura et al. 2001, Takemoto et al. 2006).