Fig. 1. Cdc2 and Aurora-A are activated by okadaic acid and microcystin. Prophase oocyte extracts were incubated at 30°C in the presence of an ATP-regenerating system and either 10^–6 M or 10^–7 M okadaic acid (OA), or 10^–6 M or 10^–7 M microcystin (MC). Samples were collected at various times either for western blotting (A) or for histone H1 and H3 kinase assays (B). (A) Western blots were analysed with the anti-Cyclin B2 antibody, the anti-Aurora-A antibody and the anti-P-Aurora-A antibody, as indicated. (B) 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.