FIG. 8.

MDC1 is required to amplify the ATM response to hypoxia. (A) U20S cells were exposed to hypoxia for 6 h and then stained for MDC1 and RPA32. (B) YZ3 (ATM^+/+) and pEBS (ATM^−/−) cells were exposed to hypoxia (Hyp) for 16 h and then stained for MDC1, γ-H2AX, and DAPI. Con, control. (C) Cells were exposed to either 6 h of hypoxia or 6 Gy. Irradiated cells were fixed 4 h after treatment. Cells were stained for MDC1 and γ-H2AX, and nuclei were visualized using DAPI. (D) MDC1^−/− and MDC1^+/+ MEFs were exposed to hypoxia, and Western blotting was carried out for the proteins indicated.