Figure 3.

Effect of p21^cip1 on MPF autoamplification. Twenty prophase oocytes were microinjected or not with p21^cip1 (1 μM). One hour later, they were microinjected with either 50 nl of cytoplasm taken from metaphase II oocytes containing active MPF (A and B) or 50 nl of 10⁻⁵ M OA (C and D). All control oocytes underwent GVBD, whereas none of the p21^cip1-injected oocytes underwent GVBD. Oocytes were collected at the time when 100% GVBD was reached in the control oocytes (3.5 h after MPF transfer or 6 h after OA injection). MPF activity was measured by assaying histone H1 kinase activity (A and C), and an amount equivalent to three oocytes was subjected to Western blot analysis for cyclin B2 (B and D). Pg, progesterone.