FIG. 3.

ATM cleavage is inhibited in vivo by the caspase inhibitor ZVAD-FMK. HL60 cells were treated with 68 μM etoposide for 4 h in the presence of the following protease inhibitors: 200 μM PMSF, 200 μM TLCK, 100 μM antipain, 200 μM E64, 200 μM leupeptin, and 20 μM ZVAD-FMK. Nuclear extracts were prepared, and 50 μg of protein was loaded per lane.