Lu Yanyan, Tao Meng, Su Hong, Tu Yiren, Wang Ji-Ping, Kuroda Masahiko, Wang Xiaozhong
Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, United States.
Department of Statistics and Data Science, Northwestern University, Evanston, IL 60208, United States.
Nucleic Acids Res. 2025 Sep 5;53(17). doi: 10.1093/nar/gkaf868.
DDX6 is known to repress messenger RNA (mRNA) translation and promote mRNA decay in microRNA-mediated silencing. In embryonic stem cells (ESCs), DDX6 primarily functions at the translation level, independent of mRNA destabilization; however, the precise molecular mechanism of how DDX6 represses translation remains unclear. Here, we identify DDX3X as a key downstream target of DDX6-mediated translational repression in ESCs. Conditional knockout of DDX3X demonstrates its essential role in microRNA (miRNA) silencing. Biochemical analyses reveal that DDX6 directly binds to DDX3X, with the C-terminal region of DDX6 being necessary for this interaction. ESCs lacking DDX6 and rescued with a DDX6 mutant that is defective in DDX3X interaction continue to exhibit miRNA silencing defects. Furthermore, the mutant DDX6 is unable to inhibit 48S preinitiation complex formation in vitro. These findings uncover a novel mechanism in which DDX6 represses target mRNA translation via its interaction with DDX3X.
已知DDX6在微小RNA介导的沉默中抑制信使核糖核酸（mRNA）翻译并促进mRNA降解。在胚胎干细胞（ESC）中，DDX6主要在翻译水平发挥作用，与mRNA去稳定化无关；然而，DDX6如何抑制翻译的精确分子机制仍不清楚。在这里，我们确定DDX3X是ESC中DDX6介导的翻译抑制的关键下游靶点。DDX3X的条件性敲除证明了其在微小RNA（miRNA）沉默中的重要作用。生化分析表明，DDX6直接与DDX3X结合，DDX6的C末端区域是这种相互作用所必需的。缺乏DDX6并用在与DDX3X相互作用方面有缺陷的DDX6突变体拯救的ESC继续表现出miRNA沉默缺陷。此外，突变的DDX6在体外无法抑制48S预起始复合物的形成。这些发现揭示了一种新机制，即DDX6通过与DDX3X相互作用抑制靶mRNA翻译。
