Table 1.

Effects of three Cdk inhibitors on early development of the X. laevis embryo

effect on:	Chk1/2	Wee1	Δ34Xic1
cleavage cycles	dose-dependent lengthening [28, 29]	modest lengthening	modest lengthening [9]
Cdk1 activity	inhibits via Tyr phosphorylation [28]	inhibits via Tyr phosphorylation [10]	no effect [38]
Cdk2 activity	inhibits via Tyr phosphorylation [29]	persists with Tyr phosphorylation	stoichiometric inhibitor [38]
degradation of cyclin E	delayed [28]	delayed	delayed [9]
degradation of Cdc25A	premature [22, 29, 32]	delayed	delayed
Cdk kinase:ppase activity at the MBT	increased kinase: decreased ppase [32, 40]	increased kinase: decreased ppase	unknown kinase: decreased ppase
effect on apoptosis	inhibits [4, 29]	activates	activates