Figure 5

Compound 13-treated cells are arrested at prometa-metaphase through the inactivation of Cdk1. HeLa S3 cells were synchronized at G2/M phase by incubating in 50 ng/ml nocodazole (noco) for 18 h. The cells were then released into complete medium at time 0 h in the absence (Sham) or presence of 10 µM compound 13. Samples were then taken at the indicated times post-nocodazole. (a) Phosphorylation of Cdk1 on Tyr15 was reduced at 1 h, but dramatically increased at 2–3 h post-nocodazole arrest point. (b) Cdk1 may be inactivated by the combination of a high level of Wee1 kinase and inactivation of Cdc25C. The relative intensity of band signals are quantified by densitometry and presented the results in Supplementary Fig. S3.