HCMV UL76 induces DNA breaks in vivo. (A) Representative images of the nucleus without comet tails (top panel) and nuclei with comet tails (lower three panels). Western blot analysis of UL76 protein levels in HEL299 (B) or COS-1 (C) cells transiently transfected with UL76-expressing plasmid at 0, 0.2, 0.5 and 1.0 μg per 6-cm dish. Cells were lysed in loading buffer, and α-tubulin was used as loading control. Quantification of HEL299 (D) or COS-1 (E) cells with fluorescent comet tails. Each data point was calculated from three independent experiments and is plotted as a percentage of the total cell population.