State Key Laboratory of Molecular Biology, Center for Excellence in Molecular Cell Science, Shanghai Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, China.
Shanghai Center for Plant Stress Biology, Chinese Academy of Sciences, Shanghai 201602, China.
J Mol Cell Biol. 2021 Aug 18;13(5):347-360. doi: 10.1093/jmcb/mjaa063.
Accumulating evidence indicates that the alternative splicing program undergoes extensive changes during cancer development and progression. The RNA-binding protein QKI-5 is frequently downregulated and exhibits anti-tumor activity in lung cancer. Howeve-r, little is known about the functional targets and regulatory mechanism of QKI-5. Here, we report that upregulation of exon 14 inclusion of cytoskeletal gene Adducin 3 (ADD3) significantly correlates with a poor prognosis in lung cancer. QKI-5 inhibits cell proliferation and migration in part through suppressing the splicing of ADD3 exon 14. Through genome-wide mapping of QKI-5 binding sites in vivo at nucleotide resolution by iCLIP-seq analysis, we found that QKI-5 regulates alternative splicing of its target mRNAs in a binding position-dependent manner. By binding to multiple sites in an upstream intron region, QKI-5 represses the splicing of ADD3 exon 14. We also identified several QKI mutations in tumors, which cause dysregulation of the splicing of QKI targets ADD3 and NUMB. Taken together, our results reveal that QKI-mediated alternative splicing of ADD3 is a key lung cancer-associated splicing event, which underlies in part the tumor suppressor function of QKI.
越来越多的证据表明，在癌症的发生和发展过程中，剪接体程序会发生广泛的变化。RNA 结合蛋白 QKI-5 在肺癌中经常下调，并表现出抗肿瘤活性。然而，关于 QKI-5 的功能靶点和调节机制知之甚少。在这里，我们报告说，细胞骨架基因 Adducin 3（ADD3）外显子 14 包含的上调与肺癌的预后不良显著相关。QKI-5 通过抑制 ADD3 外显子 14 的剪接，部分抑制细胞增殖和迁移。通过 iCLIP-seq 分析在体内以核苷酸分辨率对 QKI-5 结合位点进行全基因组作图，我们发现 QKI-5 以结合位置依赖的方式调节其靶 mRNA 的可变剪接。通过结合到上游内含子区域的多个位点，QKI-5 抑制了 ADD3 外显子 14 的剪接。我们还在肿瘤中鉴定了几个 QKI 突变，这些突变导致 QKI 靶标 ADD3 和 NUMB 的剪接失调。总之，我们的结果表明，QKI 介导的 ADD3 可变剪接是一个与肺癌相关的关键剪接事件，部分构成了 QKI 的肿瘤抑制功能。
