FIG. 1.

ATM, but not ATR, is cleaved during apoptosis in HL60 cells treated with etoposide. HL60 cells were grown in the presence of 68 μM etoposide for the times indicated. Cells were harvested, nuclear extracts were prepared, and protein (50 μg for each lane) was subjected to Western blot analysis with polyclonal rabbit anti-ATM antiserum ATM-B (A), polyclonal rabbit anti-ATR antiserum ATR-A (B), or monoclonal anti-PARP antibody PARP (C). (D) Time course of genomic DNA fragmentation in HL60 cells treated with 68 μM etoposide and visualized by ethidium bromide staining after agarose gel electrophoresis (1.5%).