Downregulation of p53-induced Mdm2 by overexpressed HIPK2. (A) Saos2 cells were transiently cotransfected with pEGFP-N and expression constructs coding for wildtype 53, wildtype HIPK2 or the kinase defective HIPK2 mutant K221A as indicated. After 24 h cells were lysed and analysed by Western blotting with the indicated antibodies. (B) GFP fluorescence was measured by quantitative fluorometry to show equal transfection efficiencies. Background fluorescence was set to 1 (lane 0). Fluorescence fold is increased above background (lanes 1 to 4). Bars, SD.