The self-splicing group II introns are bacterial and organellar ancestors of the nuclear spliceosome and retro-transposable elements of pharmacological and biotechnological importance. Integrating enzymatic, crystallographic, and simulation studies, we demonstrate how these introns recognize small molecules through their conserved active site. These RNA-binding small molecules selectively inhibit the two steps of splicing by adopting distinctive poses at different stages of catalysis, and by preventing crucial active site conformational changes that are essential for splicing progression. Our data exemplify the enormous power of RNA binders to mechanistically probe vital cellular pathways. Most importantly, by proving that the evolutionarily-conserved RNA core of splicing machines can recognize small molecules specifically, our work provides a solid basis for the rational design of splicing modulators not only against bacterial and organellar introns, but also against the human spliceosome, which is a validated drug target for the treatment of congenital diseases and cancers.

自剪接第二组内含子是核剪接体的细菌和细胞器祖先以及具有药理学和生物技术重要性的逆转录转座元件。结合酶学、晶体学和模拟研究，我们展示了这些内含子如何通过其保守的活性位点识别小分子。这些RNA结合小分子通过在不同的催化阶段采取独特的姿势，并防止剪接进程所必需的关键活性位点构象变化，选择性地抑制剪接的两个步骤。我们的数据证明了 RNA 结合剂在机械探测重要细胞通路方面的巨大力量。最重要的是，通过证明剪接机器的进化保守的RNA核心可以特异性识别小分子，我们的工作为剪接调节剂的合理设计提供了坚实的基础，不仅针对细菌和细胞器内含子，而且针对人类剪接体。是治疗先天性疾病和癌症的经过验证的药物靶点。