C MCF-7 cells were treated as indicated, and cell response to ionizing radiation were analyzed by colony formation assays (left panel). Data are presented as mean ± SEM of four independent experiments, analyzed by two-way analysis of variance (ANOVA), **P < 0.01. Knock-down efficiency of BGL3 siRNA was examined by qRT-PCR and normalized to β-Actin (middle panel), data are presented as mean ± SD of three biological replicates. Two-tailed Student's t test, **P < 0.01. Knock-down efficiency of CtIP siRNA was examined by blotting (right panel). 