Cryo-EM Structure of a Pre-catalytic Human Spliceosome Primed for Activation
Cryo-EM Structure of a Pre-catalytic Human Spliceosome Primed for Activation
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DOI：
10.1016/j.cell.2017.07.011
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发表时间：
2017-08-10
期刊：
影响因子：
64.5
通讯作者：
Stark, Holger
中科院分区：
文献类型：
--
作者：
Bertram, Karl;Agafonov, Dmitry E.;Stark, Holger
在剪接体广泛重塑为催化活性复合物之前，对剪接体的结构知之甚少。在这里，我们报告了一个三维冷冻电镜结构的前催化人类剪接体B复合物。含有U2 snRNP的头部结构域通过三个主桥连接到B复合物主体。U4/U6位于主体中的U 5三-snRNP蛋白在三-snRNP整合到B复合物中期间经历显著重排。这些包括形成部分闭合的Prp 8构象，其与Dim 1一起产生5'剪接位点（ss）结合口袋，Sad 1的置换，以及Brr 2的重排，使得其接触其U4/U6底物并准备好进行随后的剪接体活化步骤。几种B特异性蛋白质的分子组织表明它们参与负调节Brr 2、定位U6/5 'ss螺旋和稳定B复合物结构。我们的研究结果表明人类和酵母剪接体的早期激活阶段之间的显着差异。
Little is known about the spliceosome's structure before its extensive remodeling into a catalytically active complex. Here, we report a 3D cryo-EM structure of a pre-catalytic human spliceosomal B complex. The U2 snRNP-containing head domain is connected to the B complex main body via three main bridges. U4/U6. U5 tri-snRNP proteins, which are located in the main body, undergo significant rearrangements during tri-snRNP integration into the B complex. These include formation of a partially closed Prp8 conformation that creates, together with Dim1, a 5' splice site (ss) binding pocket, displacement of Sad1, and rearrangement of Brr2 such that it contacts its U4/U6 substrate and is poised for the subsequent spliceosome activation step. The molecular organization of several B-specific proteins suggests that they are involved in negatively regulating Brr2, positioning the U6/5'ss helix, and stabilizing the B complex structure. Our results indicate significant differences between the early activation phase of human and yeast spliceosomes.