FIG 1.

Cell cycle-dependent DNA damage responses. (A) Cell cycle-dependent induction of pATM after UV and NCS treatment. Each row has two cells: one S phase (EdU positive) and the other non-S phase. Merged images also have a DAPI channel shown here in blue. Images were processed the same to aid the comparison. (B) Quantification for panel A. UV-treated cells have a pATM peak in the S phase, while NCS-treated cells have pATM levels that increase with the increase in DNA content through the cell cycle. (C) Cell cycle-dependent induction of γH2AX after UV and NCS treatment. Each row has two cells: one S phase and the other non-S phase. Merged images also have a DAPI channel shown here in blue. Images were processed with the same contrast adjustments to aid the comparison. (D) Quantification for panel C. UV-treated cells have a sharp γH2AX peak in the S phase, while NCS-treated cells have pATM levels that increase with the increase in DNA content through the cell cycle. The inset compares γH2AX levels just for the control and NCS-treated cells. DNA damage in cells was caused with either 1.6 μg/ml NCS for 2 min or 10 J/m² UV, after which cells were left to recover for 60 min. Control cells were fixed right after EdU labeling. Bar graphs are normalized with respect to the mean value for G₁ phase in control cells across the populations. Error bars are standard errors of the mean. Scale bars: 10 μm. See also Fig. S1 in the supplemental material.