Figure 2.

Simultaneous depletion of ATR and ATM in HME-CC cells (ATM1-ATR) results in (A) Synthetic lethality to γ-radiation (Viability was evaluated using CellTiter-Blue viability assay kit at 48 hr post treatment) and (B) Abrogation of IR-induced G₂/M checkpoint (2 hr post treatment). Cell viability was estimated by comparing the fluorescent signal in irradiated samples to that in the time-matched control of the same cell line. Relative mitotic index was calculated by dividing the percentage of mitotic cells in the treated sample by the percentage of mitotic cells in its respective untreated sample. The data for LacZ-NS following 3 Gy of IR treatment is not showing in the graph because the measurement is 0, which means complete G₂/M checkpoint arrest. Results are presented in mean ± SE (n = 3). *means significantly different from the wild-type (LacZ-NS) (P < 0.05); **means change in cell viability due to ATM/ATR double depletion is significantly greater than the sum of that due to ATM or ATR depletion alone (P < 0.05).