Abstact

WD40 repeat-containing protein 5 (WDR5) is a core component of the SET1/mixed lineage leukemia (MLL) complex that regulates gene expression via H3K4 methylation and plays a key role in maintaining oncogenic gene expression programs, particularly in MLL1-rearranged leukemias. In this study, we leveraged a microprotein, endogenous microprotein binder of WDR5 (EMBOW), to develop peptide-based inhibitors that specifically targeted WDR5. Through comprehensive biophysical analyses and high-resolution structural studies, we revealed that EMBOW mainly bound to the WDR5 interaction (WIN) site of WDR5. Structure-guided optimization led to the development of EMBOW-derived peptides, notably Ac7, which exhibited high affinity for WDR5 (Kd = 9.17 ± 4.01 nM). These peptides effectively inhibited H3K4 methylation, suppressed oncogenic gene expression, and impeded leukemia cell proliferation in vitro. Importantly, in xenograft mouse models, Ac7 demonstrated significant anti-tumor activity with low toxicity. This work offers a promising strategy for targeting epigenetic regulators with peptide-based therapeutics, providing a foundation for innovative treatments in leukemia.