NSD3-short is an adaptor protein that couples BRD4 to the CHD8 chromatin remodeler (ChIP-Seq). Mus musculus

The bromodomain and extraterminal (BET) protein BRD4 is a therapeutic target in acute myeloid leukemia (AML). Here, we demonstrate that the AML maintenance function of BRD4 requires its interaction with NSD3, which belongs to a subfamily of H3K36 methyltransferases. Unexpectedly, AML cells were found to only require a short isoform of NSD3 that lacks the methyltransferase domain. We show that NSD3-short is an adaptor protein that sustains leukemia by linking BRD4 to the CHD8 chromatin remodeler, by using a PWWP chromatin reader module, and by employing an acidic transactivation domain. Genetic targeting of NSD3 or CHD8 mimics the phenotypic and transcriptional effects of BRD4 inhibition. Furthermore, BRD4, NSD3, and CHD8 colocalize across the AML genome, and each is released from super-enhancer regions upon chemical inhibition of BET bromodomains. These findings suggest that BET inhibitors exert therapeutic effects in leukemia by evicting BRD4-NSD3-CHD8 complexes from chromatin to suppress transcription. Overall design: ChIP-Seq for regulatory factors of BRD4, NSD3, CHD8 and histone modification H3K36me2 in MLL-AF9 transformed acute myeloid leukemia cells (RN2)

溴结构域与额外末端（BET）家族蛋白BRD4是急性髓系白血病（AML）的治疗靶点。本研究证实，BRD4维持急性髓系白血病发生发展的功能依赖于其与H3K36甲基转移酶亚家族成员NSD3的相互作用。出乎意料的是，研究发现AML细胞仅依赖缺失甲基转移酶结构域的NSD3短亚型。本研究表明，NSD3短亚型是一种衔接蛋白，通过PWWP染色质阅读器结构域将BRD4与CHD8染色质重塑因子相连，并借助酸性反式激活结构域维持白血病细胞存活。靶向NSD3或CHD8的遗传学操作可模拟BRD4抑制所产生的表型与转录效应。此外，BRD4、NSD3与CHD8在AML全基因组中共定位，且在BET溴结构域受到化学抑制时，三者均会从超级增强子区域解离。上述研究结果表明，BET抑制剂可通过将BRD4-NSD3-CHD8复合物从染色质中逐出以抑制转录，从而发挥抗白血病治疗作用。
实验整体设计：在MLL-AF9转化的急性髓系白血病细胞（RN2）中，针对BRD4、NSD3、CHD8三种调控因子以及组蛋白修饰H3K36me2开展染色质免疫共沉淀测序（ChIP-Seq）。