SCE and BRCA1 and RAD51 accumulation. (A) Sister chromatid exchange rate in parental (UT-7/P, □) and BCR-ABL–expressing cells (UT-7/9, ▪). Cells were pulsed with 5′Brdu for 24 hours and dropped on slides after hypotonic shock. SCE was revealed by Hoechst 33528 staining. The SCE rate was expressed as the average of the number of exchanged chromatid adjusted to the individual cell ploidy; error bars show 5% confidence intervals. (B) BRCA1 and RAD51 accumulation in UT-7 cell clones expressing variable levels of BCR-ABL. UT-7 clones expressing different levels of BCR-ABL were irradiated (6 Gy; +) or not (–). Six hours after irradiation 50 μg whole-cell extracts were subjected to Western blot analysis using anti-BRCA1, anti-RAD51, and anti–β-actin (lane 1, UT-7/P; lane 2, UT-7/E8-1; lane 3, UT-7/E8-2; lane 4, UT-7/9).