ABSTRACT

Paediatric cancers commonly harbour quiet mutational landscapes and are instead characterized by single driver events such as the mutation of critical chromatin regulators, expression of oncohistones, or expression of oncogenic fusion proteins. These events ultimately promote malignancy through disruption of normal gene regulation and development. The driver protein in Ewing sarcoma, EWS/FLI, is an oncogenic fusion and transcription factor that reshapes the enhancer landscape, resulting in widespread transcriptional dysregulation. Lysine-specific demethylase 1 (LSD1) is a critical functional partner for EWS/FLI as inhibition of LSD1 reverses the transcriptional activity of EWS/FLI. However, how LSD1 participates in fusion-directed epigenomic regulation and aberrant gene activation is unknown. We now show EWS/FLI causes dynamic rearrangement of LSD1 and we uncover a role for LSD1 in gene activation through colocalization at EWS/FLI binding sites throughout the genome. LSD1 is integral to the establishment of Ewing sarcoma super-enhancers at GGAA-microsatellites, which ubiquitously overlap non-microsatellite loci bound by EWS/FLI. Together, we show that EWS/FLI induces widespread changes to LSD1 distribution in a process that impacts the enhancer landscape throughout the genome.

摘要

小儿癌症通常具有安静的突变景观，而是以单一驱动事件为特征，例如关键染色质调节因子的突变、癌组蛋白的表达或致癌融合蛋白的表达。这些事件最终通过破坏正常基因调控和发育来促进恶性肿瘤。尤文肉瘤中的驱动蛋白 EWS/FLI 是一种致癌融合和转录因子，可重塑增强子景观，导致广泛的转录失调。赖氨酸特异性去甲基化酶 1 (LSD1) 是 EWS/FLI 的关键功能伙伴，因为 LSD1 的抑制会逆转 EWS/FLI 的转录活性。然而，LSD1如何参与融合导向的表观基因组调控和异常基因激活尚不清楚。我们现在展示 EWS/FLI 导致 LSD1 的动态重排，并且我们通过在整个基因组中 EWS/FLI 结合位点的共定位揭示了 LSD1 在基因激活中的作用。LSD1 是在 GGAA 微卫星上建立尤文肉瘤超增强剂不可或缺的一部分，其普遍与 EWS/FLI 结合的非微卫星基因座重叠。总之，我们表明 EWS/FLI 在影响整个基因组增强子景观的过程中引起 LSD1 分布的广泛变化。