Fig. 4

Lack of effect of p21WAF1 on sensing of DNA damage. (A) Inability of induced p21WAF1 to alter cytochrome c release into the cytosol. Inducible p21WAF1-vector (IWAF) cells either expressing (IPTG+) or not expressing (IPTG−) p21WAF1 were exposed to etoposide or control for 48 hr. Harvested cells then were separated into cytosolic and mitochondrial fractions and cytochrome c levels determined by Western blots analysis. (B) Inability of induced p21WAF1 to alter procaspase-3 cleavage. Cells transfected with control vector (Neo) or with the inducible p21WAF1 vector (IWAF) were treated with etoposide for 48 hr after preincubation with p21WAF1 inducer (IPTG) as indicated. Harvested cells were blotted with polyclonal anti-caspase-3 antibody. Uncleaved and cleaved procaspase-3 products are indicated by the upper and lower arrows, respectively. A slight residual band from p21WAF1 blotting is evident in IWAF cells exposed to IPTG.