Fig. 7.

Forced oligomerization stimulates MDM2 activity. (a) p53 was cotransfected with MDM2 and Myc-ubiquitin into H1299 cells. Polyubiquitinated p53 was detected by p53 immunoprecipitation, followed by Myc Western blotting. (b) Three tandem copies of FKBP ligand binding domain were fused to the N terminus of MDM2 to facilitate induced oligomerization by treatment with dimeric ligand AP20187. (c) p53 was cotransfected with 3× FKBP-MDM2 and Myc-ubiquitin into H1299 cells. Cells were treated with 100 nM AP20187 for 4 h. Polyubiquitinated p53 was detected by p53 immunoprecipitation, followed by Myc Western blotting. (d) p53 was cotransfected with 3× FKBP-MDM2 fusion constructs into H1299 cells. Cells were treated with 100 nM AP20187 for 16 h. p53 degradation was detected by DO-1 Western blotting.