Figure 1.

p42 MAPK requires Wee1 to effect a G2 phase arrest in Xenopus egg extracts. Cycling extracts were prepared and incubated with protein A Sepharose bound to nonimmune serum or Wee1 antibody. (A) Wee1 immunoblot of mock-depleted and Wee1-depleted extracts. (B and C) Mos-induced G2 phase arrest in mock-depleted extracts. (D and E) Failure of Wee1-depleted extracts to arrest in response to Mos. (B and D) The histone H1 kinase activities of buffer-treated (□) and Mos-treated (1 μM; ▪) extracts. (C and E) Nuclear envelope breakdown (NEBD) in the same extracts.