Fig. 8. Effect of PML depletion on UV-induced apoptosis. GM-847 cells were transfected with PML-specific siRNAs or control siRNAs (GL2) and subjected to the indicated doses of UV irradiation on day 3 following transfection. Subsequent to irradiation, cells were incubated in the absence or in the presence of 4 mM caffeine for 2 hours prior to analysis. (A,B) Cells were fixed, stained with Hoechst and evaluated by immunofluorescence microscopy for the presence or absence of condensed chromatin. For each sample, more than 500 cells were evaluated. The data represents the mean ± s.d. of two independent experiments. (C,D) Analysis of apoptotic DNA fragmentation by pulse field gel electrophoresis. The 50-300 kb apoptotic DNA fragments are indicated.