患乳酸脱氢酶基因H3林氨酸27位甲硫氨酸（H3K27M）变异的BMG（包括弥漫性固有脑桥胶质母细胞瘤（DIPG）的BMG）是致命的儿童脑部癌症。这些肿瘤具有H3K27me3基因转录抑制标记的全局降低，伴随着转录激活标记H3K27ac的增加。我们假设，除了改变H3K27修饰外，H3K27M突变还重新编程了主要染色质重塑开关/蔗糖不发酵（SWI/SNF）复合物。SWI/SNF复合物可存在两种主要形式，称为BAF和PBAF，它们在神经发育和癌症中起着核心作用。此外，BAF拮抗PRC2，这是催化H3K27me3的主要酶。我们证明， H3K27M BMG显示SWI / SNF复合物ATP酶亚单位SMARCA4和SMARCA2以及PBAF组分PBRM1的蛋白质水平增加。此外，突变H3K27M的沉默降低了SMARCA4蛋白水平。同时，针对SMARCA4、SMARCA2和PBRM1的蛋白靶向嵌合体（PROTAC）AU-15330对H3.3K27M细胞表现出细胞毒性，但不影响H3野生型细胞。AU-15330在无启动子区域测得的ATAC-Seq中降低了染色质可及性和全球H3K27ac水平。在AU-15330处理的细胞中进行的基因表达、蛋白质组学和染色质可及性综合分析表明降低了FOXO1的水平，它是转录因子Foxhead家族的关键成员。此外，基因或药物对FOXO1的靶向可导致H3K27M细胞死亡。总的来说，我们的结果表明，H3K27M上调了SMARCA4水平，针对H3.3K27M中SWI/SNF ATP酶的联合靶向可作为这些致命性儿童脑部肿瘤的强大治疗策略。

Diffuse midline gliomas (DMGs) including diffuse intrinsic pontine gliomas (DIPGs) bearing lysine-to-methionine mutations in histone H3 at lysine 27 (H3K27M) are lethal childhood brain cancers. These tumors harbor a global reduction in the transcriptional repressive mark H3K27me3 accompanied by an increase in the transcriptional activation mark H3K27ac. We postulated that H3K27M mutations, in addition to altering H3K27 modifications, reprogram the master chromatin remodeling switch/sucrose nonfermentable (SWI/SNF) complex. The SWI/SNF complex can exist in two main forms termed BAF and PBAF that play central roles in neurodevelopment and cancer. Moreover, BAF antagonizes PRC2, the main enzyme catalyzing H3K27me3. We demonstrate that H3K27M gliomas show increased protein levels of the SWI/SNF complex ATPase subunits SMARCA4 and SMARCA2, and the PBAF component PBRM1. Additionally, knockdown of mutant H3K27M lowered SMARCA4 protein levels. The proteolysis targeting chimera (PROTAC) AU-15330 that simultaneously targets SMARCA4, SMARCA2, and PBRM1 for degradation exhibits cytotoxicity in H3.3K27M but not H3 wild-type cells. AU-15330 lowered chromatin accessibility measured by ATAC-Seq at nonpromoter regions and reduced global H3K27ac levels. Integrated analysis of gene expression, proteomics, and chromatin accessibility in AU-15330-treated cells demonstrated reduction in the levels of FOXO1, a key member of the forkhead family of transcription factors. Moreover, genetic or pharmacologic targeting of FOXO1 resulted in cell death in H3K27M cells. Overall, our results suggest that H3K27M up-regulates SMARCA4 levels and combined targeting of SWI/SNF ATPases in H3.3K27M can serve as a potent therapeutic strategy for these deadly childhood brain tumors.