FIGURE 1.

CTF-induced apoptosis is transcription-dependent. A–C, HeLa cells were transiently transfected with a CTF-ER construct. A, after 12 h of transfection, cells were treated with DMSO (left panel) or 4-OHT (right panel) for 4 h, fixed, and processed for immunofluorescence microscopy. Bar, 10 μm. B, cells were pretreated for 4 h with the indicated RNA polymerase inhibitors and induced for 8 h with 4-OHT followed by staining with Annexin V and FACS analysis. C, cells were pretreated for 4 h with α-amanitin and induced with 4-OHT for 8 h, lysed, and run on SDS-PAGE. Protein levels of PARP and actin were detected by Western blot and quantified using the TINA 2.09 software program. Apoptotic index was obtained by dividing the intensity of the cleaved PARP band (p85) at the indicated time over the intensity at time 0. D, HeLa cells were transiently transfected with the indicated Gal4-tagged constructs and a luciferase reporter containing the Gal4 DNA binding element. A pRSV40-β-galactosidase construct was co-transfected as a control. After 18 h, cells were lysed and luciferase activity measured with a luminometer. Luciferase activity was normalized to β-galactosidase activity and fold-luciferase activity obtained by dividing values with the value obtained for Gal4 alone. *, p < 0.03, Student's t test.