Fig. 3. Identification of PP1 as a likely Nek2 antagonist. (A) U2OS cells were treated for 1 hour with the indicated concentrations of okadaic acid or caliculin A. Then, centrosome splitting was analyzed as described. As a positive control, Nek2-transfected cells were examined in parallel. (B) U2OS cells were transfected with PP1, either alone or in combination with Nek2, Cdk2/cyclin E or Cdk2/cyclin A, and the extent of centrosome splitting was determined.