Nature | 研究揭示髓母细胞瘤常见突变的致癌机制
专业点燃希望约 6 分钟深度突变扫描：绘制了KBTBD4 癌症热点的突变图，揭示了插入和替换可以促进功能获得的不同偏好以及热点相互作用中有关的关键残基。KBTBD4的癌症突变通过直接靶向HDAC1/2，促进CoREST（一种控制染色质可及性和转录的复合物）的降解，这种降解会改变表观遗传程序，进而改变转录程序，促进癌细胞干细胞的增加，从而驱动肿瘤发生。
冷冻电子显微镜分析：对与 LSD1–HDAC1–CoREST （LHC 综合体）结合的两个不同 KBTBD4 癌症突变体的低温电子显微镜分析表明，KBTBD4 同型二聚体与 HDAC1 不对称地结合，具有两个 KELCH 重复的β-螺旋结构域。髓母细胞瘤突变稳定了 HDAC1 和其中一个 KBTBD4 β-螺旋之间的界面，使一个庞大的侧链插入 HDAC1 活性位点。
药物干预实验：结构和深度突变扫描结果表明KBTBD4 MB 突变体通过去乙酰化酶活性位点的热点相互作用直接与 HDAC1/2 结合，从而促进 CoREST 降解。这些观察结果意味着HDAC1/2 活性位点抑制剂可以在空间上阻断突变连接酶的结合，从而阻断其致癌功能。突变型KBTBD4-HDAC1 与与辛二酰苯胺羟肟酸 (SAHA) 结合的 HDAC2 的叠加分析支持这一观点，即 HDAC1/2 抑制剂和插入的精氨酸残基可能会发生位置冲突。用SAHA，CI-994（一种 2-氨基苯甲酰胺衍生的抑制剂）和RBC1HI（新型 HDAC1/HDAC2 抑制剂，Regenacy Brain I 类 HDAC 抑制剂）进行试验， 证明了这三种抑制剂可以保全由两种突变KBTBD4-P 和 KBTBD4-PR 表达引起的 CoREST 降解， 如图2所示。
撰文
责编
制作
排版 | 车洁 校对 | uu
延伸阅读
*本文由深圳市拾玉儿童公益基金会“儿童肿瘤前沿”团队编译或约稿，文中图表均源引自文献原文。本文著作权归文章作者所有，欢迎个人转发分享，未经允许禁止转载，作者拥有所有法定权利，违者必究。如需转载，请留言或联系[email protected]。本文旨在分享儿童肿瘤科研前沿成果，不是治疗方案推荐。如需获得疾病治疗方案指导，请前往正规医院就诊。
▼滑动查看更多▼
原文摘要（Abstract）
Cancer mutations can create neomorphic protein-protein interactions to drive aberrant function1,2. As a substrate receptor of the CULLIN3-RING E3 ubiquitin ligase complex, KBTBD4 is recurrently mutated in medulloblastoma3, the most common embryonal brain tumour in children4. These mutations impart gain-of-function to KBTBD4 to induce aberrant degradation of the transcriptional corepressor CoREST5. However, their mechanism remains unresolved. Here we establish that KBTBD4 mutations promote CoREST degradation through engaging HDAC1/2 as the direct target of the mutant substrate receptor. Using deep mutational scanning, we chart the mutational landscape of the KBTBD4 cancer hotspot, revealing distinct preferences by which insertions and substitutions can promote gain-of-function and the critical residues involved in the hotspot interaction. Cryo-electron microscopy analysis of two distinct KBTBD4 cancer mutants bound to LSD1-HDAC1-CoREST reveals that a KBTBD4 homodimer asymmetrically engages HDAC1 with two KELCH-repeat β-propeller domains. The interface between HDAC1 and one of the KBTBD4 β-propellers is stabilized by the medulloblastoma mutations, which insert a bulky side chain into the HDAC1 active site pocket. Our structural and mutational analyses inform how this hotspot E3-neosubstrate interface can be chemically modulated. First, we unveil a converging shape-complementarity-based mechanism between gain-of-function E3 mutations and a molecular glue degrader, UM171. Second, we demonstrate that HDAC1/2 inhibitors can block the mutant KBTBD4-HDAC1 interface and proliferation of KBTBD4-mutant medulloblastoma cells. Altogether, our work reveals the structural and mechanistic basis of cancer mutation-driven neomorphic protein-protein interactions.
DOI: 10.1038/s41586-024-08533-3