Dependence of Mos-induced Cdc2 activation on MAP kinase function in a cell-free system

The progression of G(2)-arrested Xenopus laevis oocytes into meiotic M-phase is accompanied by the nearly simultaneous activation of p42 MAP kinase and Cdc2/cyclin B, This timing raises the possibility that the activation of one kinase might depend upon the other, Here we have examined whether Cdc2 activation requires p42 MAP kinase function. We have reconstituted Mos-induced Cdc2 activation in cell-free Xenopus oocyte extracts, and have found that Mos-induced Cdc2 activation requires active p42 MAP kinase, is inhibited by a MAP kinase phosphatase and is independent of protein synthesis. These findings indicate that p42 MAP kinase is an essential component of the M phase trigger in this system.