WIN site inhibition disrupts a subset of WDR5 function

Andrew J Siladi,Andrea C Florian,April M Weissmiller,Stephen W Fesik,Lance R Thomas,Qi Liu,Shelly L Lorey,Joy H Creighton,Brittany K Matlock,Jing Wang,David K Flaherty,Gregory C Howard,William P Tansey

doi:10.1038/s41598-022-05947-9

Andrew J Siladi, Andrea C Florian + Show 11 more

Open Access

https://doi.org/10.1038/s41598-022-05947-9

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Abstract

WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes. WDR5 is also a prominent target for pharmacological inhibition in cancer. Small-molecule degraders of WDR5 have been described, but most drug discovery efforts center on blocking the WIN site of WDR5, an arginine binding cavity that engages MLL/SET enzymes that deposit histone H3 lysine 4 methylation (H3K4me). Therapeutic application of WIN site inhibitors is complicated by the disparate functions of WDR5, but is generally guided by two assumptions—that WIN site inhibitors disable all functions of WDR5, and that changes in H3K4me drive the transcriptional response of cancer cells to WIN site blockade. Here, we test these assumptions by comparing the impact of WIN site inhibition versus WDR5 degradation on H3K4me and transcriptional processes. We show that WIN site inhibition disables only a specific subset of WDR5 activity, and that H3K4me changes induced by WDR5 depletion do not explain accompanying transcriptional responses. These data recast WIN site inhibitors as selective loss-of-function agents, contradict H3K4me as a relevant mechanism of action for WDR5 inhibitors, and indicate distinct clinical applications of WIN site inhibitors and WDR5 degraders.

Highlights

WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes
We engineered Ramos cells so that WDR5 could be degraded via an auxininducible degron (AID)[30] (Supplementary Fig. S1), creating the line we refer to as “AIDW”
Regardless, upon addition of indole-3-acetic acid (IAA), tagged WDR5 is rapidly depleted from AIDW cells, but not wild-type (WT) Ramos cells (Fig. 1a)

Summary

Introduction

WDR5 nucleates the assembly of histone-modifying complexes and acts outside this context in a range of chromatin-centric processes. We show that WIN site inhibition disables only a specific subset of WDR5 activity, and that H3K4me changes induced by WDR5 depletion do not explain accompanying transcriptional responses These data recast WIN site inhibitors as selective loss-of-function agents, contradict H3K4me as a relevant mechanism of action for WDR5 inhibitors, and indicate distinct clinical applications of WIN site inhibitors and WDR5 degraders. We report that WIN site inhibitor impacts only a subset of transcriptional events controlled by WDR5, and show that the influence of WDR5 on transcription is not explained via its role in H3K4 methylation These findings reveal that WDR5 loss cannot be used to model the effects of WIN site inhibitors on cancer cells, show how an essential protein can be partially inhibited to induce a pro-therapeutic response, and support distinct applications of WIN site inhibitors and WDR5 degraders in the clinic

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Conclusion