Fig. 3. Removal of PP2A is sufficient to lead to Cdc2 and Aurora-A activation. Prophase oocyte extracts were incubated in the absence or in the presence of microcystin-agarose beads. The extracts were then incubated at 30°C in the presence or in the absence (–) of an ATP-regenerating system (ATP) with or without okadaic acid (OA). Samples were collected at various times either for histone H1 and H3 kinase assays (A) or for western blotting (B). (A) Samples were pulled down on p13 beads and assayed for Cdc2 kinase activity using histone H1 as substrate, or immunoprecipitated with the anti-Aurora-A antibody and assayed for Aurora-A kinase activity using histone H3 peptide as substrate. Cdc2 and Aurora-A kinase activities are expressed in cpm incorporated in the substrate. (B) Western blots were analysed with the anti-Cyclin B2 antibody, the anti-Aurora-A antibody, the anti-P-Aurora-A antibody, the anti-PP1 antibody and the anti-PP2A antibodies as indicated.