MBoC | ARTICLE

ABSTRACT The activity of Cdk1–cyclin B1 mitotic complexes is regulated by the balance between the counteracting activities of Wee1/Myt1 kinases and Cdc25 phosphatases. These kinases and phosphatases must be strictly regulated to ensure proper mitotic timing. One masterpiece of this regulatory network is Cdk1, which promotes Cdc25 activity and sup-presses inhibitory Wee1/Myt1 kinases through direct phosphorylation. The Cdk1-dependent phosphorylation of Wee1 primes phosphorylation by additional kinases such as Plk1, trigger-ing Wee1 degradation at the onset of mitosis. Here we report that Cdc14A plays an impor-tant role in the regulation of Wee1 stability. Depletion of Cdc14A results in a significant re-duction in Wee1 protein levels. Cdc14A binds to Wee1 at its amino-terminal domain and reverses CDK-mediated Wee1 phosphorylation. In particular, we found that Cdc14A inhibits Wee1 degradation through the dephosphorylation of Ser-123 and Ser-139 residues. Thus the lack of phosphorylation of these two residues prevents the interaction with Plk1 and the con-sequent efficient Wee1 degradation at the onset of mitosis. These data support the hypoth-esis that Cdc14A counteracts Cdk1–cyclin B1 activity through Wee1 dephosphorylation