Figure 5.

Plx1 is required for activation of Cdc25C and the G₂/M transition. Prophase extracts were treated with either control IgG- or anti-Plx1-coupled beads as described in MATERIALS AND METHODS. The extract supernatants were then supplemented with either PKI or PKI plus recombinant Plx1 (25 μg/ml final concentration), and samples were frozen at the indicated times and analyzed. (A) Samples were immunoblotted for Plx1 before immunodepletion (Start) and after treatment with control IgG- or anti-Plx1–coupled beads (IgG and antibody [Ab], respectively) at the indicated times. Samples were also assayed for histone H1 kinase activity (B) or immunoblotted for Cdc25C, Mos, and pMAPK (C). A sample of the Plx1 preparation was subjected to SDS-PAGE and Coomassie blue staining to assess its purity (B, right).