Fig. 1. Formation of ssDNA foci in GM-847 cells in response to UV-irradiation. GM-847 cells metabolically labeled for 24 hours with BrdU were subjected to 10 J/m2 UV-irradiation and subsequently incubated for 1 or 2 hours in the presence or absence of 4 mM caffeine. (A) Representative immunofluorescence images of non-irradiated cells containing ssDNA-positive APBs and UV-irradiated and caffeine-treated cells containing UV-induced ssDNA foci. (B) Quantitative determination of cells containing ssDNA-foci. For each sample, more than 500 cells were scored. Average of two independent experiments ± standard deviation (s.d.) is shown. (C) Quantitative determination of cells exhibiting co-localization between TRF2 and ssDNA-containing foci. For each sample, 50 cells that contained ssDNA foci were evaluated. Average of two independent experiments ± s.d. is shown. (NI) Non-irradiated.