Figure 4.

Cdh1 protects Ku80 at DSBs in G1 phase. (A, B) The accumulation of Ku80 at sites of DNA damage. (A) U2OS cells were transfected with indicated siRNA and next day treated with lovastatin for 2 days. Then, cells were subjected to microirradiation and immunostaining of Ku80 and γH2AX was performed at 1 h, 2.5 h and 4 h after microirradiation. (B) Quantification of Ku80 intensity at microirradiated regions shown in (A) (n > 80). (C) Analysis of cell cycle arrest in cells treated with lovastatin. U2OS cells were treated as indicated in (A) and then cell cycle analysis was performed. (D) The efficiency of siRNA-mediated target gene knockdown was shown by Western Blot analysis. (E) Regulation of Ku80 dissociation from chromatin after DNA damage. U2OS cells were transfected with indicated siRNAs and treated with lovastatin. After isolation of soluble and chromatin fractions, the expression of indicated proteins was measured by Western blot analysis. Error bars indicate SEM from three independent experiments. Scale bars represent 10 μm.