Targeted Degradation of PRC1 Components, BMI1 and RING1B, via a Novel Protein Complex Degrader Strategy

Abstract

Polycomb repressive complex 1 (PRC1) is an essential epigenetic regulator that mainly controls histone H2A Lys119 mono‐ubiquitination (H2AK119ub). B cell‐specific Moloney murine leukemia virus Integration site 1 (BMI1) and really interesting new gene 1B (RING1B) are PRC1 core components and play critical roles in the development of various cancers. However, therapeutic agents targeting PRC1 are very limited. In this study, MS147, the first degrader of PRC1 core components, BMI1 and RING1B, is discovered via a novel protein complex degradation strategy that utilizes the target protein's interacting partner protein (embryonic ectoderm development (EED)). MS147, which comprises an EED small‐molecule binder linked to a ligand of the E3 ligase von Hippel‐Lindau (VHL), degrades BMI1/RING1B in an EED‐, VHL‐, ubiquitination‐, and time‐dependent manner. MS147 preferentially degrades BMI1/RING1B over polycomb repressive complex 2 (PRC2) core components. Consequently, MS147 effectively reduces H2AK119ub, but not histone H3 Lys27 tri‐methylation (H3K27me3), which is catalyzed by PRC2. Furthermore, MS147 effectively inhibits the proliferation of cancer cell lines that are insensitive to PRC2 inhibitors/degraders. Overall, this study provides a novel BMI1/RING1B degrader, which is a useful chemical tool to further investigate the roles of PRC1 in cancer, and a novel protein complex degradation strategy, which can potentially expand the degradable human proteome.

Acetylation Targeting Chimera Enables Acetylation of the Tumor Suppressor p53

“…The RT-qPCR was performed as previously described. , Briefly, NCI-H1299 p53Y220C stable cells were treated with DMSO or 10 μM PK9328, compound 17 , or MS78 for 24 h. Total RNA was extracted using the Monarch Total RNA Miniprep Kit (T2010S, New England Biolabs), and cDNA was generated using the SuperScript IV First-Strand Synthesis System (18091050, Thermo Fisher). qPCR was performed using the PowerUp SYBR Green Master Mix (Thermo Fisher Scientific, A25742) on an Agilent Technologies Stratagene Mx3005p qPCR system.…”

Discovery and Characterization of a Novel Cereblon-Recruiting PRC1 Bridged PROTAC Degrader

“…Previously reported intermediate 10 was substituted with tert-Butyl N-(4-bromobutyl)carbamate followed by de-Boc protection under acid condition to yield intermediate 11. 11 Regular peptide coupling reaction between intermediate 11 and pomalidomide tethered with various linkers yielded compounds 1−9. 20 Effect of Compounds 1−9 on Degrading PRC1 Components BMI1 and RING1B.…”

“…10 Employing the same strategy, we also discovered a novel polycomb repressive complex 1 (PRC1) degrader, MS147, an EED-binding, and VHL-recruiting PROTAC, which degraded the PRC1 core components, B cell-specific Moloney murine leukemia virus integration site 1 (BMI1), and really interesting new gene 1B (RING1B), through the interaction with EED. 11 While EED is a core component of the polycomb repressive complex 2 (PRC2), it has been shown that the N-terminus of EED interacts with BMI1 and RING1B and can regulate the PRC1 enzymatic activity, catalyzing monoubiquitination of histone H2A lysine 119 (H2AK119ub). 12,13 However, traditional EED-binding PROTAC degraders, such as UNC6852, 14 Protac 1 and 2, 15 and UNC7700 (Figure 1), 16 degraded PRC2 subunits, enhancer of zeste homologue 2 (EZH2), and suppressor of zeste-12 (SUZ12), as a consequence of the direct degradation of EED.…”

“…On the other hand, our PRC1 bridged PROTAC, MS147 (Figure 1), preferentially degraded BMI1 and RING1B over EED and other PRC2 core components in an EED-, VHL-, and UPS-dependent manner and was much more effective in suppressing the proliferation of multiple EZH2insensitive cancer cell lines. 11 It is important to note that the VHL E3 ligase was utilized in both bridged PROTAC cases (MS28 and MS147), and whether other E3 ubiquitin ligases . Chemical structures of previously reported EED-binding PROTAC degraders.…”

Chemically induced degradation of epigenetic targets

“…Park et al developed MS147 , an EED-binding, VHL-recruiting PROTAC, which degrades PRC1 core components, BMI1 and RING1B, preferentially over EED. 126 Very recently, Xiong et al from the same research group reported the concept of Bridged PROTAC in which the first-in-class degrader of Cyclin D1, MS28 utilized CDK4/6-binding PROTAC to preferentially degrade Cyclin D1 taking advantage of the CDK4/6-Cyclin D1 interaction. 127 It is important to note that Cylin D1 does not have a known small molecule binder or inhibitor rendering it undruggable but the Bridge PROTAC, MS28 allowed it to be targeted and degraded.…”