Identification of a Structural Determinant for Selective Targeting of HDMX

• Published in: Structure (London) 2020-07, Vol.28 (7), p.847-857.e5
• Main Authors: Ben-Nun, Yael, Seo, Hyuk-Soo, Harvey, Edward P., Hauseman, Zachary J., Wales, Thomas E., Newman, Catherine E., Cathcart, Ann M., Engen, John R., Dhe-Paganon, Sirano, Walensky, Loren D.
• Format: Article
• Language: English
• Subjects: cancer; HDM2/MDM2; HDMX/MDMX/MDM4; p53; SAH-p53; selective; stapled peptide; structure; targeting; therapeutic
• ISSN: 0969-2126; 1878-4186
• DOI: 10.1016/j.str.2020.04.011

p53 is a critical tumor-suppressor protein that guards the human genome against mutations by inducing cell-cycle arrest or apoptosis. Cancer cells subvert p53 by deletion, mutation, or overexpression of the negative regulators HDM2 and HDMX. For tumors that retain wild-type p53, its reactivation by pharmacologic targeting of HDM2 and/or HDMX represents a promising strategy, with a series of selective small-molecule HDM2 inhibitors and a dual HDM2/HDMX stapled-peptide inhibitor being evaluated in clinical trials. Because selective HDM2 targeting can cause hematologic toxicity, selective HDMX inhibitors could provide an alternative p53-reactivation strategy, but clinical candidates remain elusive. Here, we applied a mutation-scanning approach to uncover p53-based stapled peptides that are selective for HDMX. Crystal structures of stapled-peptide/HDMX complexes revealed a molecular mechanism for the observed specificity, which was validated by HDMX mutagenesis. Thus, we provide a blueprint for the development of HDMX-selective inhibitors to dissect and target the p53/HDMX interaction. [Display omitted] •Cancer cells can subvert wild-type p53 by expression of HDM2 and HDMX•HDM2 and dual inhibitors are in trials but selective HDMX agents are lacking•Scanning mutagenesis of a stapled p53 peptide identified HDMX-selective constructs•Structures of the complexes revealed a mechanism for HDMX-binding selectivity Ben-Nun et al. performed scanning mutagenesis of a stapled-peptide dual inhibitor of HDM2/HDMX to identify mutations that conferred HDMX selectivity. Structures of L26E-mutant constructs in complex with HDMX revealed the molecular basis for binding selectivity. Stapled-peptide libraries can provide key structure-function insights, such as this blueprint for developing selective HDMX inhibitors.