Figure 6.

Degradation of XIAP during apoptosis is cIAP1-dependent. (A) HeLa cells were treated simultaneously with cisplatin and ALLN, each at 20 μM, for 24 h. (B) After 16 h of 10 μM doxorubicin exposure, HeLa cells were treated with 10 μM lactacystin for an additional 8 h. (C–F) HeLa cells were transfected with the nontargeting luciferase (NT) and cIAP1-specific and cIAP2-specific (duplexes “2” and “9”) siRNA for 48 h, and then transfected cells were exposed to 20 μM cisplatin (C and D) or 10 μM doxorubicin (E and F) for 24 h. (G) HeLa cells were transfected with the nontargeting luciferase (NT), E1-specific or dually with E1- and cIAP1-specific siRNA for 80 h, and then transfected cells were exposed to 20 μM cisplatin for 24 h. Proteins were extracted and subjected to Western immunoblot analysis. cIAP1 and cIAP2 were recognized by an anti-RIAP1 antibody that cross-reacts with both proteins.