FIGURE 4.

CPT induces single-strand breaks in a transcription- and proteasome-dependent manner in quiescent WI-38 cells. a, WI-38 cells cultured in DMEM supplemented with 0.2% serum were pretreated with APH (10 μm), DRB (150 μm), or MG132 (2 μm) for 30 min, followed by co-treatment with CPT (25 μm) for 1 h. SSBs were analyzed by alkaline comet assay as described under “Experimental Procedures.” Left panel, representative comet images. Right panel, the histogram of the tail moment plotted against each treatment condition. b, WI-38 cells cultured in DMEM supplemented with 0.2% serum were treated with Me₂SO or CPT (25 μm) for 1 h. DSBs were analyzed by neutral comet assay as described under “Experimental Procedures.” Upper panel, representative comet images. Lower panel, the histogram of the tail moment.