Figure 14: Nuclear vs. extra-nuclear effects of p53 stabilization [56]. MDM2 binds to p53, ubiquitinates it and leads to proteasomal degradation of p53. Nutlin, a MDM2 antagonist, binds to MDM2 and prevents it from down regulating p53 levels through proteasomal degradation, and increases levels of p53, which in turn induces apoptosis.