美国华盛顿大学郑宁研究组近日取得一项新成果。经过不懈努力，他们研究出UM171粘附不对称的CRL3-HDAC1/2组装以降解CoREST协抑制子。该项研究成果发表在2025年2月12日出版的《自然》上。

在这里，研究组发现UM171作为一种分子胶，诱导KBTBD4和HDAC1/2之间的高亲和力相互作用，以促进协同抑制因子的降解。通过蛋白质组学和化学抑制剂研究，研究小组确定UM171的主要靶点是HDAC1/2。低温电子显微镜分析结合UM171和LSD1-HDAC1-CoREST复合物的二聚体KBTBD4发现了一个不对称组装，其中单个UM171分子使一对KELCH-repeat螺旋桨结构域招募HDAC1催化结构域。一个KBTBD4螺旋桨部分掩盖了HDAC1活性位点的边缘，UM171利用它来扩展E3-neosubstrate接口。另一个推进器通过一个不同的接口协同加强HDAC1的结合。

CoREST-HDAC1/2-KBTBD4整体相互作用进一步得到内源性辅助因子肌醇己基磷酸的支持，该因子作为第二分子胶。利用KBTBD4和HDAC1的碱基编辑器扫描证实了四元配合物相互作用表面的功能相关性。通过描述UM171的直接靶点及其作用机制，该研究团队揭示了二聚体CRL3 E3提供的协同性如何被小分子降解剂利用。

据了解，UM171是一种有效的体外人造血干细胞自我更新激动剂。UM171通过选择CUL3-RING E3泛素连接酶（CRL3）复合物的底物受体KBTBD4，促进LSD1-CoREST共抑制物复合物的降解，从而限制造血干细胞的磨损。然而，UM171的直接作用靶点和作用机制尚不清楚。

附：英文原文

Title: UM171 glues asymmetric CRL3–HDAC1/2 assembly to degrade CoREST corepressors

Author: Yeo, Megan J. R., Zhang, Olivia, Xie, Xiaowen, Nam, Eunju, Payne, N. Connor, Gosavi, Pallavi M., Kwok, Hui Si, Iram, Irtiza, Lee, Ceejay, Li, Jiaming, Chen, Nicholas J., Nguyen, Khanh, Jiang, Hanjie, Wang, Zhipeng A., Lee, Kwangwoon, Mao, Haibin, Harry, Stefan A., Barakat, Idris A., Takahashi, Mariko, Waterbury, Amanda L., Barone, Marco, Mattevi, Andrea, Carr, Steven A., Udeshi, Namrata D., Bar-Peled, Liron, Cole, Philip A., Mazitschek, Ralph, Liau, Brian B., Zheng, Ning

Issue&Volume: 2025-02-12

Abstract: UM171 is a potent agonist of ex vivo human haematopoietic stem cell self-renewal1. By co-opting KBTBD4, a substrate receptor of the CUL3–RING E3 ubiquitin ligase (CRL3) complex, UM171 promotes the degradation of the LSD1–CoREST corepressor complex, thereby limiting haematopoietic stem cell attrition2,3. However, the direct target and mechanism of action of UM171 remain unclear. Here we show that UM171 acts as a molecular glue to induce high-affinity interactions between KBTBD4 and HDAC1/2 to promote corepressor degradation. Through proteomics and chemical inhibitor studies, we identify the principal target of UM171 as HDAC1/2. Cryo-electron microscopy analysis of dimeric KBTBD4 bound to UM171 and the LSD1–HDAC1–CoREST complex identifies an asymmetric assembly in which a single UM171 molecule enables a pair of KELCH-repeat propeller domains to recruit the HDAC1 catalytic domain. One KBTBD4 propeller partially masks the rim of the HDAC1 active site, which is exploited by UM171 to extend the E3–neosubstrate interface. The other propeller cooperatively strengthens HDAC1 binding through a distinct interface. The overall CoREST–HDAC1/2–KBTBD4 interaction is further buttressed by the endogenous cofactor inositol hexakisphosphate, which acts as a second molecular glue. The functional relevance of the quaternary complex interaction surfaces is demonstrated by base editor scanning of KBTBD4 and HDAC1. By delineating the direct target of UM171 and its mechanism of action, we reveal how the cooperativity offered by a dimeric CRL3 E3 can be leveraged by a small molecule degrader.

DOI: 10.1038/s41586-024-08532-4

Source: https://www.nature.com/articles/s41586-024-08532-4