Figure 3

MK-1775 treatment abrogates the G2/M cell cycle checkpoint. CTS cells (Panels A and B) or U937 cells (Panels C and D) were treated with 500 nM MK-1775 for up to 48 h. Samples were taken at the indicated time points and fixed with ethanol for PI staining and cell cycle analysis (Panels A and C). Whole cell lysates were subjected to Western blotting and probed with anti-p-CDK1, -CDK1, -p-CDK2, -CDK2, -CHK1, -pCHK1, -p-cdc25c, -γH2AX, or -β-actin antibody (Panels B and D).