Figure 7.

Synthesis and degradation of cyclin B1. (A) Twenty prophase oocytes were microinjected or not with p21^cip1 (1 μM) and incubated or not in the presence of cycloheximide (CHX) at 100 μg/ml for 1 h before progesterone (Pg) addition. Oocytes were cultured overnight, collected, homogenized, and analyzed by Western blotting for cyclin B1. An amount equivalent to two oocytes was loaded on each lane. (B) Stability of microinjected cyclin B1. Seventy oocytes were microinjected or not with p21^cip1 (1 μM), microinjected with [³⁵S]methionine-labeled cyclin B1, and incubated in the presence or absence of progesterone. Ten oocytes of each group were collected at different times, homogenized, and analyzed by autoradiography. An amount equivalent to four oocytes was loaded on each lane. (C) Extracts from B (lower left panel) were analyzed by Western blotting for cyclin B1. An amount equivalent to two oocytes was loaded on each lane.