FIGURE 8.

A, comet assay of 4pX-1 cells grown with (+) or without (-) pX expression for 12 and 24 h. Arrows point to DNA tailing, indicative of DNA damage. Quantification of cells displaying DNA tailing is from three independent experiments, counting a total of 600 cells. B, 4pX-1 cells synchronized in G₁/S by the double thymidine block were immunostained for BrdUrd incorporation (green) and γH2AX (red), 5 and 10 h after release from the block, with (+) or without (-) pX expression. BrdUrd (BrdU) was added 30 min before fixation. Images shown are by confocal microscopy. The right panel shows quantification of BrdUrd-positive (green) and γH2AX-positive (red) 4pX-1 cells by ImageJ software, counting at least 1000 cells for each histogram. C, confocal microscopy of mitotic 4pX-1 cells at 10 h after release from the double thymidine block with pX expression using the indicated markers.