Effect of DNA damage on p53 and apoptosis in E2F-1–overexpressing cells.
DNA damage upregulates p53 and induces apoptosis in E2F-1–overexpressing cells. (A) p53 immunoblot. Cells were exposed to UV irradiation (25 J/m2) or camptothecin (1-hour pulse, 100 mM) in the presence of IL-3 and then washed extensively and cultured for a further 11 hours in IL-3 medium. Lane 1 shows cells at baseline; lane 2, cells after 12 hours' culture in IL-3 with 0.05% dimethyl sulfoxide, 3 to 12 hours after UV irradiation and 4 to 11 hours after being pulsed with camptothecin. (B) Cells were cultured in IL-3 medium, washed, and resuspended in 10% FBS/phenol-free RPMI for irradiation (10 J/cm2). Cells were then cultured for a further 24 hours in IL-3 medium. As a mock treatment, cells were not irradiated. Cell cycle analysis was performed by flow cytometry.
