MDM2 and Hao-Fountain syndrome: Deletion or mutation of USP7 leads to HAFOUS, a disorder characterized by aggressive behavior, intellectual disability, and developmental delay.253 USP7 primarily targets the Ub ligase MDM2, which facilitates p53 ubiquitination and degradation.525 By inhibiting MDM2 self-ubiquitination, USP7 stabilizes MDM2, thus enhancing MDM2-mediated p53 degradation.525 Therefore, targeting USP7 for inhibition has emerged as a potential strategy for tumor suppression.