Arsenic Trioxide Rescues Structural p53 Mutations through a Cryptic Allosteric Site

Major challenges in drugging p53 mutations include heterogeneous mechanisms of inactivation and the absence of broadly-applicable allosteric sites. Here we report the identification of small molecules including arsenic trioxide (ATO), an established agent in treating acute promyelocytic leukemia, as cysteine-reactive compounds that rescue structural p53 mutations.

Crystal structures of arsenic-bound p53 mutants reveal a cryptic allosteric site involving three arsenic coordinating cysteines within the DNA-binding domain, distal to the zinc-binding site. Arsenic binding stabilizes the DNA-binding loop-sheet-helix motif alongside the overall β-sandwich fold, endowing p53 mutants with thermostability and transcriptional activity. In cellular and mouse xenograft models, ATO reactivates mutant p53 for tumor suppression.