Figure 2

Phosphorylation of H2AX in response to radiation-induced DNA damage in the presence or absence of DNA-PKcs and ATM. A, B: Phosphorylated H2AX (γH2AX) levels in DNA-PKcs depleted HeLa-H1 (A), HepG2-H1 [39] (B) cells and the control HeLa-NC or HepG2-NC cells. Cells were harvested at 0, 0.25, 1, 4 and 10 h after 4 Gy γ-irradiation. Protein expression was assayed by Western blotting. C: Expression of phospho-ATM at Ser-1981 detected at 0.5 h after 4 Gy γ-irradiation. D, E: H2AX phosphorylation in ATM-deficient cells AT5BIVA (D) and ATS4 (E) after 4 Gy γ-irradiation. Cells were harvested at 0, 0.25, 1, 4 and 10 h post-irradiation, and protein expression was assayed by Western blotting. F, G: The effect of the PI3K inhibitor wortmannin (F) and the DNA-PKcs specific inhibitor NU7026 (G) on H2AX phosphorylation in AT5BIVA cells after γ-irradiation. AT5BIVA cells were pretreated with 2 μM wortmannin or 10 μM NU7026 for 2 h, then irradiated with 4 Gy. The cells were harvested at 0, 0.25, 1 and 4 h after irradiation. Protein expression was assayed by Western blotting. H: The effect of NU7026 treatment (10 μM) on H2AX phosphorylation in HeLa-NC cells after 4 Gy irradiation.