Apoptosis following treatment of BEAC cells with telomerase siRNAs. SEG-1 cells, transfected with control (Cont) or telomerase specific (Tel) siRNAs were cultured for three weeks and analyzed for apoptosis by evaluating annexin labeling or cleavage of PARP. A. Cells were mixed with annexin V-BIOTIN and treated sequentially with streptavidin conjugated to fluorescein isothiocyanate (FITC) and propidium iodide (PI). Apoptotic cells within the same microscopic field were viewed and photographed by phase contrast (PC) or by fluorescence emitted at 518 nm (FITC filter). Using the FITC filter, early apoptotic cells (positive for Annexin V-Biotin-FITC staining) appear bright green. B. SEG-1 cells were treated exactly as described for panel A and analysed for cleavage of poly(ADP-ribose) polymerase (PARP), a marker for apoptosis. PARP was identified by western blotting using a rabbit polyclonal antibody against PARP (Santa Cruz). C. Bar graph showing percentage of PARP found to be cleaved in cells treated with control or telomerase siRNAs.