Fig 1. RAD18 is involved in IR-induced activation of the G2/M phase cell cycle checkpoint.

(A) HT1080 human cancer cells were transfected with si-ctrl or si-RAD18. After 48 hrs, the expression levels of RAD18 in the insoluble fractions were determined by western blotting. (B) Cell proliferation was measured in si-ctrl and si-RAD18 treated cells. Each value represents the mean (+standard deviation) of the results from three independent experiments. (C) Cells were exposed to 4Gy IR, fixed at the indicated time points after irradiation, stained with propidium iodide (PI), and the cell cycle distributions were determined by flow cytometry. (D) Cells were exposed to 1, 2, and 4 Gy IR, and then fixed at 6 hrs after irradiation. Fixed cells were stained with PI and analyzed by flow cytometry.