Fig. 6. Apoptosis in normal and XP8BR cells after UVB irradiation. Cells were irradiated with 100 J/m² UVB and at various times after irradiation apoptosis was measured either using the Apoptag kit (A) or by the cleavage of PARP (B). In the latter experiments, sonicated cell lysates were electrophoresed in SDS–PAGE gels and the gels analysed by Western blotting using an antibody specific for the 85 kDa cleavage product of PARP.