Intron recognition in the spotlight Excision of noncoding introns from pre–messenger RNAs is catalyzed by the spliceosome, a large RNA-protein complex that recognizes specific sequences at the exon-intron boundaries (splice sites). These sequences are highly degenerate in humans, and it has remained elusive how they are recognized by the spliceosome. Tholen et al . report a series of high-resolution structures of the human U2 small nucleolar ribonucleoprotein, the component of the spliceosome that recognizes branch sites. The structures explain how SF3B6 helps to stabilize the branch helix in the absence of extensive sequence complementarity. A newly identified spliceosome assembly intermediate suggests a mechanism for fidelity control of branch site recognition. —DJ

中文翻译：

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人类剪接体识别分支位点的结构基础

内含子识别成为焦点 从前信使 RNA 中切除非编码内含子是由剪接体催化的，剪接体是一种大型 RNA-蛋白质复合物，可识别外显子-内含子边界（剪接位点）的特定序列。这些序列在人类中是高度简并的，并且剪接体如何识别它们仍然难以捉摸。托伦等人。报道了人类 U2 小核仁核糖核蛋白的一系列高分辨率结构，该蛋白是识别分支位点的剪接体的组成部分。这些结构解释了 SF3B6 如何在缺乏广泛序列互补性的情况下帮助稳定分支螺旋。新鉴定的剪接体组装中间体提出了分支位点识别保真度控制的机制。——DJ