Fig. 5. A model for roles of 14-3-3 proteins in Drosophila cell division. In interphase, 14-3-3 proteins and cyclin A/Cdk1 and cyclin B/Cdk1 complexes are predominantly cytoplasmic. Here, 14-3-3
acts to keep Cdk1 in check, preventing mitosis in normal or irradiated embryos. As Cdk1 becomes active (owing to the accumulation of its activator Stg or after recovery from DNA damage) and cells enter mitosis, accumulating cyclin/Cdk1 activity promotes and maintains 14-3-3 protein localization near chromosomes. Upon the transition to anaphase, the localized 14-3-3 proteins, and 14-3-3
in particular, can contribute to the rapid, effective inactivation of the cyclin/Cdk1. Thus, in interphase, 14-3-3 can act to keep Cdk1 inactive in the cytoplasm but, once Cdk1 is active, it can act in turn to localize 14-3-3 proteins in preparation for their action during the exit from mitosis.
