Figure 4.

BMI1 focal accumulation is independent of ATM, NBS1, or Mdc1. A–C, Analysis of human fibroblasts deficient for ATM (A), MEFs deficient for Mdc1 (B), or immortalized human lymphocytes deficient for NBS1 (C). Wild-type or mutant cells were irradiated at 5 Gy and labeled with a BMI1 antibody. Focal accumulation of BMI1 was observed in ATM^−/−, Mdc1^−/−, and NBS1^−/− cells. C, Western blot analysis confirmed NBS1 deficiency in NBS1-mutant cells. D, GBM cells irradiated at 3 Gy were fixed at different time point after IR and labeled with BMI1, p-ATM, MDC1, γH2AX, and Mre11 antibodies. Note that the recruitment of BMI1 precedes that of p-ATM, MDC1, or Mre11. The cell lines used were GBM0811 and GBM2002.