PP2A-B56 and PP2A-B55 are phosphatases for Cdc20 T70. (A) Cells treated with a control RNAi oligo or a pool of B56 RNAi oligoes targeting all isoforms were arrested in nocodazole and Cdc20 immunopurified. Samples were analyzed by Western blot for Cdc20 T70p and APC3 T447p as well as APC3 and BubR1. The degree of Cdc20 T70p and APC3 T447p was determined by normalizing to pan-Cdc20 or pan-APC3 signals. (B and C) A nocodazole lysate was prepared and treated with the indicated phosphatase inhibitors (see also Fig.1 A) for 5 or 15 min as indicated. Cdc20 or APC4 was immunopurified and the level of Cdc20 T70p and APC3 T447p determined. For all experiments, three independent experiments were conducted and quantified. Ctrl, control.