WARTS tumor suppressor is phosphorylated by Cdc2/cyclin B at spindle poles during mitosis

Identification of physiological substrates for Cdc2/ cyclin B is crucial for understanding the functional link between mitotic events and Cdc2/cyclin B activation. A human homologue of the Drosophila warts tumor suppressor, termed WARTS, is a serine/threonine kinase and a dynamic component of the mitotic apparatus. We have found that Cdc2/cyclin B forms a complex with a fraction of WARTS in the centrosome and phosphorylates the Ser613 site of WARTS during mitosis. Immunocytochemical analysis has shown that the S613-phosphorylated WARTS appears in the spindle poles at prometaphase and disappears at telophase. Our findings suggest that Cdc/cyclin B regulates functions of WARTS on the mitotic apparatus. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.