Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, North Carolina.
Department of Biochemistry and Biophysics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina.
Cancer Res. 2019 Jul 15;79(14):3583-3594. doi: 10.1158/0008-5472.CAN-18-3275. Epub 2019 Jun 4.
Mutation of DNA methyltransferase 3A at arginine 882 (DNMT3A) is prevalent in hematologic cancers and disorders. Recently, DNMT3A has been shown to have hypomorphic, dominant-negative, and/or gain-of-function effects on DNA methylation under different biological contexts. However, the causal role for such a multifaceted effect of DNMT3A in leukemogenesis remains undetermined. Here, we report TF-1 leukemia cells as a robust system useful for modeling the DNMT3A-dependent transformation and for dissecting the cause-effect relationship between multifaceted activities of DNMT3A and leukemic transformation. Ectopic expression of DNMT3A and not wild-type DNMT3A promoted TF-1 cell transformation characterized by cytokine-independent growth, and induces CpG hypomethylation predominantly at enhancers. This effect was dose dependent, acted synergistically with the isocitrate dehydrogenase 1 (IDH1) mutation, and resembled what was seen in human leukemia patients carrying DNMT3A. The transformation- and hypomethylation-inducing capacities of DNMT3A relied on a motif involved in heterodimerization, whereas its various chromatin-binding domains were dispensable. Mutation of the heterodimerization motif that interferes with DNMT3A binding to endogenous wild-type DNMT proteins partially reversed the CpG hypomethylation phenotype caused by DNMT3A, thus supporting a dominant-negative mechanism in cells. In mice, bromodomain inhibition repressed gene-activation events downstream of DNMT3A-induced CpG hypomethylation, thereby suppressing leukemogenesis mediated by DNMT3A. Collectively, this study reports a model system useful for studying DNMT3A, shows a requirement of the dominant-negative effect by DNMT3A for leukemogenesis, and describes an attractive strategy for the treatment of leukemias carrying DNMT3A. SIGNIFICANCE: These findings highlight a model system to study the functional impact of a hotspot mutation of DNMT3A at R882 in leukemia.
DNA 甲基转移酶 3A 第 882 位精氨酸突变（DNMT3A）在血液系统癌症和疾病中普遍存在。最近，在不同的生物学背景下，DNMT3A 被证明对 DNA 甲基化具有低功能、显性负效应和/或获得功能效应。然而，DNMT3A 这种多方面效应在白血病发生中的因果作用仍未确定。在这里，我们报告 TF-1 白血病细胞作为一种有用的强大系统，可用于模拟 DNMT3A 依赖性转化，并剖析 DNMT3A 的多方面活性与白血病转化之间的因果关系。DNMT3A 的异位表达而非野生型 DNMT3A 促进 TF-1 细胞转化，表现为细胞因子非依赖性生长，并诱导增强子处的 CpG 低甲基化。这种效应是剂量依赖性的，与异柠檬酸脱氢酶 1（IDH1）突变协同作用，并类似于携带 DNMT3A 的人类白血病患者中所见。DNMT3A 的转化和低甲基化诱导能力依赖于涉及异二聚化的基序，而其各种染色质结合结构域则是可有可无的。干扰 DNMT3A 与内源性野生型 DNMT 蛋白结合的异二聚化基序突变部分逆转了由 DNMT3A 引起的 CpG 低甲基化表型，因此在细胞中支持显性负效应机制。在小鼠中，溴结构域抑制抑制了 DNMT3A 诱导的 CpG 低甲基化下游的基因激活事件，从而抑制了由 DNMT3A 介导的白血病发生。总的来说，这项研究报告了一个有用的研究 DNMT3A 的模型系统，表明 DNMT3A 对白血病发生的显性负效应的必要性，并描述了一种有吸引力的治疗携带 DNMT3A 的白血病的策略。意义：这些发现突出了一个模型系统，用于研究 DNMT3A 中 R882 热点突变对白血病的功能影响。
