Oxygen and nutrient deprivation are common features of solid tumors. Although abnormal alternative splicing (AS) has been found to be an important driving force in tumor pathogenesis and progression, the regulatory mechanisms of AS that underly the adaptation of cancer cells to harsh microenvironments remain unclear. Here, we found that hypoxia- and nutrient deprivation–induced asparagine endopeptidase (AEP) specifically cleaved DDX3X in a HIF1A-dependent manner. This cleavage yields truncated carboxyl-terminal DDX3X (tDDX3X-C), which translocates and aggregates in the nucleus. Unlike intact DDX3X, nuclear tDDX3X-C complexes with an array of splicing factors and induces AS events of many pre-mRNAs; for example, enhanced exon skipping (ES) in exon 2 of the classic tumor suppressor PRDM2 leads to a frameshift mutation of PRDM2. Intriguingly, the isoform ARRB1-Δexon 13 binds to glycolytic enzymes and regulates glycolysis. By utilizing in vitro assays, glioblastoma organoids, and animal models, we revealed that AEP/tDDX3X-C promoted tumor malignancy via these isoforms. More importantly, high AEP/tDDX3X-C/ARRB1-Δexon 13 in cancerous tissues was tightly associated with poor patient prognosis. Overall, our discovery of the effect of AEP-cleaved DDX3X switching on alternative RNA splicing events identifies a mechanism in which cancer cells adapt to oxygen and nutrient shortages and provides potential diagnostic and/or therapeutic targets.

中文翻译：

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AEP 裂解的 DDX3X 诱导替代 RNA 剪接事件以介导癌细胞在恶劣微环境中的适应


氧气和营养缺乏是实体瘤的共同特征。尽管异常选择性剪接（AS）已被发现是肿瘤发病和进展的重要驱动力，但AS对癌细胞适应恶劣微环境的调节机制仍不清楚。在这里，我们发现缺氧和营养剥夺诱导的天冬酰胺内肽酶 (AEP) 以 HIF1A 依赖性方式特异性裂解 DDX3X。这种裂解产生截短的羧基末端 DDX3X (tDDX3X-C)，它在细胞核中易位并聚集。与完整的 DDX3X 不同，核 tDDX3X-C 与一系列剪接因子复合并诱导许多前 mRNA 的 AS 事件；例如，经典肿瘤抑制因子PRDM2的外显子2中增强的外显子跳跃（ES）导致PRDM2的移码突变。有趣的是，异构体 ARRB1-Δ 外显子 13 与糖酵解酶结合并调节糖酵解。通过利用体外测定、胶质母细胞瘤类器官和动物模型，我们发现 AEP/tDDX3X-C 通过这些异构体促进肿瘤恶性。更重要的是，癌组织中的高 AEP/tDDX3X-C/ ARRB1- Δ外显子 13与患者预后不良密切相关。总体而言，我们发现 AEP 切割的 DDX3X 开关对替代 RNA 剪接事件的影响确定了癌细胞适应氧气和营养短缺的机制，并提供了潜在的诊断和/或治疗靶点。