Figure 1.
Induction of SCFβ-TrCP-dependent degradation of Xe-Cdc25A by the ERK pathway. (A) Artificially activated eggs (or eggs after 40 min of calcium ionophore treatment) were injected or not with 9 ng of JNK mRNA, reinjected 2.5 h later (time 0) with 9 ng of either MEK-CA, MKK6-CA, or MKK7-CA mRNAs, and analyzed at 20-min intervals by immunoblotting (IB) with anti-Xe-Cdc25A, anti-phospho-JNK, anti-phospho-ERK, and anti-phospho-p38 antibodies. (B) Activated eggs were injected with 9 ng of GST mRNA (Control) or MEK-CA mRNA. Egg extracts were then treated (+λ) or not (−λ) with λ phosphatase and analyzed for Xe-Cdc25A by immunoblotting. (C) Activated eggs were injected with 18 ng of GST mRNA (Control) or dominant-negative β-TrCPΔF mRNA, reinjected 2.5 h later with 9 ng of MEK-CA mRNA, and then analyzed for Xe-Cdc25A by immunoblotting. (D) Activated eggs were injected or not with 9 ng of MKP3 mRNA, reinjected 40 min later with 2 ng of mRNA encoding Myc-tagged WT or D231A Xe-Cdc25A, further injected 2.5 h later with 9 ng of MEK-CA mRNA, and then analyzed for Myc-Xe-Cdc25A constructs and phospho-ERK by immunoblotting. Five, three, four, and four independent experiments were performed for A, B, C, and D, respectively, and, for each, a typical result is shown.