Figure 5

Effects of inhibitors of Cdk activity on early development of X. laevis. (A) Exogenous Chk1/2 indirectly inhibits Cdk1 and Cdk2 by targeting Cdc25A for degradation. Onset of the MBT is delayed, but development proceeds without apoptosis. (B) Exogenous Wee1 phosphorylates Cdk1 and Cdk2. The total pool of Cdk1 activity is inhibited. Onset of the MBT including degradation of Cdc25A is delayed. Embryos die by apoptosis during early gastrulation. (C) Exogenous Δ34-Xic1 inhibits Cdk2 but not Cdk1. Like Wee1, Δ34-Xic1 delays the MBT including degradation of Cdc25A, and induces apoptosis.