法国欧洲分子生物学实验室Wojciech P. Galej研究组揭示剪接体识别分支位点的结构基础。这一研究成果发表在2021年11月25日出版的国际学术期刊《科学》上。

他们分离了人类 17S U2 snRNP，并在体外重建了其依赖于 ATP 的重塑和与前 mRNA 底物的结合。 他们确定了一系列高分辨率 (2.0-2.2 Å) 结构，提供了分支位点 (BS)选择过程的快照。与底物结合的 U2 snRNP 表明 SF3B6 稳定了 BS:U2 snRNA 双链体，这有助于结合序列互补性较差的内含子。与底物结合分离的 ATP 依赖性重塑以与 BS 识别竞争的构象捕获U2 snRNA，提供基于分支螺旋稳定性的选择机制。

据介绍，U2 snRNP 识别内含子BS是剪接体组装过程中的关键事件。在哺乳动物中，BS 序列的保守性较差，仅通过碱基配对机制无法实现明确的内含子识别。

附：英文原文

Title: Structural basis of branch site recognition by the human spliceosome

Author: Jonas Tholen, Michal Razew, Felix Weis, Wojciech P. Galej

Issue&Volume: 2021-11-25

Abstract: Recognition of the intron branch site (BS) by the U2 snRNP is a critical event during spliceosome assembly. In mammals, BS sequences are poorly conserved and unambiguous intron recognition cannot be achieved solely via a base-pairing mechanism. We isolated human 17S U2 snRNP and reconstituted in vitro its ATP-dependent remodeling and binding to the pre-mRNA substrate. We determined a series of high-resolution (2.0-2.2 ) structures providing snapshots of the BS selection process. The substrate-bound U2 snRNP shows that SF3B6 stabilizes the BS:U2 snRNA duplex, which could aid binding of introns with poor sequence complementarity. ATP-dependent remodeling uncoupled from substrate binding captures U2 snRNA in a conformation that competes with BS recognition, providing a selection mechanism based on branch helix stability.

DOI: abm4245

Source: https://www.science.org/doi/10.1126/science.abm4245