Fig. 5.

Kinetochore function is required for PP2A^B56 recognition by Cdc20. (A) Depletion of Kif18A increases phosphorylation of Ser92 of Cdc20. Asynchronous HeLa cells were treated with indicated siRNAs, and endogenous Cdc20 was purified using monoclonal αCdc20 antibodies. Phosphorylation of Cdc20^S92 was determined by Western blot analysis. (B) Depletion of Knl1 interferes with Cdc20 binding to BubR1, PP2A^B56, and Ube2S. HeLa cells were depleted of Knl1, synchronized in prometaphase, and treated with MG-132 as indicated. Cdc20 was purified using specific antibodies and analyzed for binding partners by Western blot analysis. (C) Model of Ube2S regulation by reversible phosphorylation.