Fig. 4.

HOXB9-expressing cells exhibit rapid ATM activation and early termination of DDR. (A) MCF10A cells expressing LacZ or HOXB9 were irradiated (10 Gy), and pATM and MDC1 expression were visualized 0, 10, and 30 min after γ-irradiation (IR). Bar graphs show the percentage of nuclei positive for pATM or MDC1. The mean was derived from the percentage of cells that scored positive for pATM or MDC1 across nine fields. (Scale bar, 10 μM.) (B) pATM is elevated in HOXB9-expressing cells. Western blot analysis of pATM expression in MCF10A cells expressing LacZ (LZ) or HOXB9 (B9) after 0, 10, and 30 min of irradiation. (C) MCF10A cells expressing HOXB9 were treated with KU55933 (10 μM) for 2 h before irradiation. The inhibitor was washed out, and γ-H2AX expression (Left) and 53BP1 expression (Right) was visualized 0, 5, 10, and 30 min after γ-irradiation. (D) Western blot analysis of γ-H2AX expression in MCF10A cells expressing LacZ or HOXB9 after 0, 12, and 24 h of γ-irradiation.