Figure 2.

Mos functions as an MAP kinase activator in starfish oocytes. (A) Dynamics of Mos and MAP kinase through starfish meiotic cycles. At the female pronucleus (FP) stage after the completion of meiosis II, mature eggs were fertilized, resulting in the disappearance of Mos. P-MAPK, antiphospho MAP kinase corresponding to its active form; PB 1 and 2, the first and the second polar bodies, respectively. (B) MAP kinase activation induced by injection of the GST-starfish Mos fusion protein into immature starfish oocytes. Oocytes were injected with various amounts of GST-Mos and recovered at 30 min for immunoblots. (C) Antisense mos prevents MAP kinase activation after 1-MeAde addition in starfish oocytes. Immature oocytes were injected with various amounts of antisense and sense mos oligonucleotides and then treated with 1-MeAde to undergo GVBD. Oocytes were recovered for immunoblots 60 min after 1-MeAde addition. Mos synthesis was undetectable at 35 pg injection of antisense mos. Upper and lower bands of MAP kinase (indicated by arrows) correspond to the active and the inactive forms, respectively (see ref. 19).