MDM2 and ataxia telangiectasia: In addition, USP7 may deubiquitinate p53 via Mdm2.31 However, upon DNA damage, ataxia telangiectasia mutated-dependent phosphorylation of Mdm2 decreased the binding affinity between USP7 and Mdm2, tilting the balance towards p53 stabilization.31, 32, 33, 34