Discovery of a 53BP1 Small Molecule Antagonist Using a Focused DNA-Encoded Library Screen
Devan J. Shell, Caroline A. Foley, Qinhong Wang, Chelsea M. Smith, Shiva Krishna Reddy Guduru, Hong Zeng, Aiping Dong, Jacqueline L. Norris‐Drouin, Matthew Axtman, P. Brian Hardy, Gaorav P. Gupta, Levon Halabelian, Stephen V. Frye, Lindsey I. James, Kenneth H. Pearce
Abstract
Methyl-lysine reader p53 binding protein 1 (53BP1) is a central mediator of DNA break repair and is associated with various human diseases, including cancer. Thus, high-quality 53BP1 chemical probes can aid in further understanding the role of 53BP1 in genome repair pathways. Herein, we utilized focused DNA-encoded library screening to identify the novel hit compound UNC8531, which binds the 53BP1 tandem Tudor domain (TTD) with an IC 50 of 0.47 ± 0.09 μM in a TR-FRET assay and K d values of 0.85 ± 0.17 and 0.79 ± 0.52 μM in ITC and SPR, respectively. UNC8531 was cocrystallized with the 53BP1 TTD to guide further optimization efforts, leading to UNC9512. NanoBRET and 53BP1-dependent foci formation experiments confirmed cellular target engagement. These results show that UNC9512 is a best-in-class small molecule 53BP1 antagonist that can aid further studies investigating the role of 53BP1 in DNA repair, gene editing, and oncogenesis.