Figure 5
Phosphorylation of Cdc25A, B, and C by Cdk2-Speedy/Ringo A2. (A) Potential CDK phosphorylation sites in human Cdc25A, B, and C. There are 12 (S/T)PXX sequences in Cdc25A, 14 in Cdc25B, and 6 in Cdc25C. The two sequences that come closest to fitting the consensus CDK phosphorylation sequence (S/T)PX(K/R) are underlined. (B) Phosphorylation of Cdc25A, B, and C by K2A2coexp and [pT160]Cdk2-cyclin A. Phosphorylation of GST-Cdc25A, B, and C (5 μg) by the indicated amounts of K2A2coexp (lanes 1–6) or Cdk2-cyclin A (lanes 7–12). Phosphorylated proteins were separated by SDS-PAGE and detected by autoradiography. (C) Phosphorylation of histone H1 by K2A2coexp and [pT160]Cdk2-cyclin A. Histone H1 (5 μM) was phosphorylated by the indicated amounts of K2A2coexp (lanes 1–6) or Cdk2-cyclin A (lanes 7–12). Phosphorylated proteins were separated by SDS-PAGE and detected by autoradiography.