Abstract
One of the profound changes in cellular morphology which occur during mitosis is a massive alteration in the organization of the microfilament cytoskeleton. These changes, together with other mitotic events including nuclear membrane breakdown, chromosome condensation, and formation of mitotic spindles, are all induced by a single molecular complex called MPF, maturation promoting factor. We have demonstrated that cdc2 kinase, a catalytic subunit of MPF, phosphorylates nonmuscle caldesmon both in vivo and in vitro, which causes caldesmon to dissociate from microfilaments during mitosis. Our results suggest that cdc2 kinase directly controls microfilament re-organization during mitosis because caldesmon inhibits actomyosin ATPase.
