BRCA2-depleted cells exhibit an additive repair defect by pre-IR.

A) Pre-IR treatment increases the fraction of BRCA2-knockdown cells with a DNA repair defect. 1BR hTERT cells treated with siControl or siBRCA2 were irradiated with 0.2 Gy X-rays 48 h after siRNA transfection. At 6 h after pre-IR, cells were irradiated with 2 Gy X-rays (challenge IR), and APH was added immediately after the challenge IR. γH2AX foci in G2 cells (CENPF+) were scored. Representative images of G2 cells are shown in S2A Fig. Error bars represent the SD of three independent experiments. B) Knockdown efficiency of BRCA2 is shown. Arrowhead indicates BRCA2. C) Representative images of the increase in the proportion of BRCA2-depleted cells with a DSB repair defect following pre-IR. Scale bar represent 10 μm (for all images).