Figure 4.

Expression of xCdc7 during oocyte maturation. Resting oocytes (stage VI) were stimulated by progesterone and analyzed by gel electrophoresis according to the method of Anderson et al. (ref. 37; see Materials and Methods) and immunoblotting at the indicated times. Germinal vesicle breakdown occurred at about 4 hours. After 8 hours (approximately meiosis II), the remaining oocytes were treated with calcium ionophore to simulate fertilization. Embryos expressing a Flag-tagged form of xCdc7 (1 kDa greater predicted molecular mass) are indicated by “Flag- xCdc7”. (A) Anti-xCdc7 immunoblot; (B) Same blot as A, reprobed with antibodies to Mos^Xe.