FIG. 6.

MAPK signaling is not sufficient to stimulate endogenous cyclin B1 mRNA polyadenylation in the absence of MPF activity. (A) Immature oocytes in 1% DMSO were pretreated for 1 h with 100 μM MEK inhibitor (MI), as indicated, and then stimulated with progesterone or left untreated (Imm). When the oocytes had reached GVBD₅₀, pools were taken and total RNA was extracted. Endogenous cyclin B1 mRNA polyadenylation was analyzed by separating total RNA on a 1% agarose gel and hybridizing with a probe specific for cyclin B1. The migration of endogenous cyclin B1 mRNA is shown by the bracket. (B) Immature oocytes were injected with GST 107Wee RNA, as indicated, and left for 14 h to express the protein. The oocytes were then either stimulated with progesterone (Prog) or injected with RNA encoding GST Mos. Pools of oocytes were harvested when the progesterone and GST Mos-injected oocytes were fully mature (GVBD_>90), and total RNA was extracted. Polyadenylation of endogenous cyclin B1 mRNA was analyzed as described above. The dashed line acts as a reference point: RNAs migrating under the line are not polyadenylated, and RNAs migrating above the line are polyadenylated.