33258 Hoechst enhancement of the photosensitivity of bromodeoxyuridine-substituted cells

Cells that have incorporated 5-bromodeoxyuridine (BrdU) into their DNA become extremely sensitive to photoinduced killing after treatment with the dye, 33258 Hoechst. Under appropriate conditions the dye increases the efficiency of killing by a factor of approximately 10(4). This enhanced photosensitivity suggests that the combination of BrdU, dye, and light can be used to select conditional lethal mutants.