Functional G2 damage checkpoint in DT40 cells deleted for cCdc14A, cCdc14B, or Cdh1. (A) Flow cytometry analysis of the indicated cell lines incubated with Noco for 8 h with or without prior IR (IR + Noco and Noco). Cells were stained with PI and for pH3 to measure the MI. Values normalized to the MI of the corresponding Noco-treated cultures (n = 3). (B) Synchrony in G2 at the time of IR. (C) Cells synchronized in G2 were exposed to IR. Cells were harvested, and MI was measured by flow cytometry (n = 3). (D) Cells were irradiated, fixed (12 h after treatment), and stained for γ-tubulin (green) and centrin (red). The number of cells with more than two centrosomes was scored. Bar, 5 µm. (E) Quantification of phenotype in D (n = 3; 100 cells per each cell line) is shown. (F, top) WT, cCdc14A-KO, and cCdc14B-KO cells were analyzed by IB. (bottom) Quantification of Chk1(S345ph) before (t = 0) and after IR. Chk1(S345ph) was normalized to Chk1. Chk1(S345ph) in the untreated WT sample was set to 1 (n = 2). Error bars indicate mean ± SD.