Artemis and DDB2 regulate p27 protein levels through the Cul4A-based E3 ligase complex. (A) Artemis and DDB2 are required for p27 degradation by the Cul4A-based E3 ligase complex. HeLa cells were transfected with control, Artemis or DDB2 siRNAs. After 24 h, cells were transfected with the indicated DNa, and 24 h later, cells were harvested for immunoblot analysis. (B) Cul4A is required for Artemis or DDB2-mediated p27 degradation. HeLa cells were transfected with control or Cul4A siRNAs, and 24 h later, cells were transfected with the indicated DNA. Cells were harvested after an additional 24 h for immunoblot analysis.