Figure 6.

Analysis of Xe-Wee1 tyrosine phosphorylation in the first three mitotic cycles and in the first mitotic cycle with nondegradable Mos. Untreated eggs (A–D) and eggs that had been injected with wild-type nondegradable Mos (E–H) were activated with calcium ionophore and the progression through the cell cycle was monitored by histone H1 kinase activity (A,E). The levels of endogenous Mos and nondegradable Mos were detected by immunoblotting (B,F; one egg per lane). The level of tyrosine phosphorylated Cdc2 was determined following precipitation with p13/suc1 beads and immunoblotting with anti-phosphotyrosine antibody (C,G, top; 10 eggs per precipitate). The levels of Cdc2 in the p13 /suc1 precipitates are also shown (C,G, bottom). The levels of tyrosine-phosphorylated Xe-Wee1 were detected following immunoprecipitation with anti-Xe-Wee1 antibodies and immunoblotting with anti-phosphotyrosine antibody 4G10 (D,H; 10 eggs per precipitate).