Discovery of first-in-class inhibitors of the TRF1:TIN2 protein:protein interaction by fragment screening.

The study identifies a compound that binds to TRF1 with a K_D of 29 µM and shows potential to disrupt the TRF1:TIN2 interaction, but further research is needed to assess clinical relevance.

Summary and findings

This study reports the discovery of inhibitors targeting the TRF1:TIN2 protein interaction, which is essential for the recruitment of TRF1 to the shelterin complex. The binding affinity of the lead compound (compound 40) to TRF1 was measured at a K_D of 29 µM. Additionally, the compound demonstrated an IC₅₀ of 67 µM in displacing a TIN2 probe.

Abstract

TRF1 is a subunit of the shelterin complex that binds to and protects the linear ends of chromosomes known as telomeres. Both genetic deletion and chemical inhibition of TRF1 have been shown to block the growth of lung carcinoma, glioblastoma, and renal cell carcinoma in mice without affecting mouse survival or tissue function, making TRF1 a potential therapeutic target in cancer^1-3. Here, we report the discovery of a series of fragment hits that bind at the interface between the TRFH domain of TRF1 (TRF1_TRFH) and a peptide of TIN2 (TIN2_TBM), an interaction essential for the recruitment of TRF1 to shelterin, using X-ray crystallography (XChem) and ligand-observed NMR (LO-NMR) fragment screening. We discovered a first-in-class inhibitor of the TRF1:TIN2 interaction (compound 40) that binds to TRF1_TRFH with a K_D of 29 µM (95% CI: 20-41 µM), displaces a TIN2 probe with an IC₅₀ of 67 µM (95% CI: 10-120 µM), and expels TRF1 from purified shelterin. Aided by a novel crystal system of TRF1_TRFH, we characterised fragments binding in a hotspot at the TRF1:TIN2 interface; these will serve as a starting point for the structure-guided development of potent inhibitors of TRF1 protein:protein interactions to disrupt shelterin complex assembly.

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