PHD3 Regulates p53 Protein Stability by Hydroxylating Proline 359

Cellular p53 protein levels are regulated by a ubiquitination/de-ubiquitination cycle that can target the protein for proteasomal destruction. The ubiquitination reaction is catalyzed by a multitude of ligases, whereas the removal of ubiquitin chains is mediated by two deubiquitinating enzymes (DUBs), USP7 (HAUSP) and USP10. Here, we show that PHD3 hydroxylates p53 at proline 359, a residue that is in the p53-DUB binding domain. Hydroxylation of p53 upon proline 359 regulates its interaction with USP7 and USP10, and its inhibition decreases the association of p53 with USP7/USP10, increases p53 ubiquitination, and rapidly reduces p53 protein levels independently of mRNA expression. Our results show that p53 is a PHD3 substrate and that hydroxylation by PHD3 regulates p53 protein stability through modulation of ubiquitination. [Display omitted] •PHD3 hydroxylates p53 on Pro359•Hydroxylated Pro359 forms a binding site for USP7/10•Hydroxylase inhibition reduces USP binding and enhances p53 ubiquitination•p53 protein stability and signaling regulated by PHD3 activity It has been known for decades that hypoxia regulates p53 signaling. Rodriguez et al. here uncover a direct mechanism of how p53 protein stability is regulated by oxygen-sensing enzymes through a post-translational modification.