Hu Yan, Hou Yan, Zhou Shijie, Wang Yingzhi, Shen Congcong, Mu Li, Su Dan, Zhang Rundong
Department of Ophthalmology, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu 610041, P.R. China.
State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu 610041, P.R. China.
iScience. 2023 Aug 12;26(9):107604. doi: 10.1016/j.isci.2023.107604. eCollection 2023 Sep 15.
The spliceosomal snRNP cores, each comprised of a snRNA and a seven-membered Sm ring (D1/D2/F/E/G/D3/B), are assembled by twelve chaperoning proteins in human. However, only six assembly-assisting proteins, ICln and the SMN complex (SMN/Gemin2/Gemin6-8), have been found in (Sp). Here, we used recombinant proteins to reconstitute the chaperone machinery and investigated the roles of these proteins systematically. We found that, like the human system, the assembly in requires ICln and the SMN complex sequentially. However, there are several significant differences. For instance, h_F/E/G forms heterohexamers and heterotrimers, while Sp_F/E/G only forms heterohexamers; h_Gemin2 alone can bind D1/D2/F/E/G, but Sp_Gemin2 cannot. Moreover, we found that Sp_Gemin2 is essential using genetic approaches. These mechanistic studies reveal that these six proteins are necessary and sufficient for Sm core assembly at the molecular level, and enrich our understanding of the chaperone systems in species variation and evolution.
剪接体snRNP核心由一个snRNA和一个七元Sm环（D1/D2/F/E/G/D3/B）组成，在人类中由12种伴侣蛋白组装而成。然而，在（某种生物，原文未明确写出）中仅发现了六种组装辅助蛋白，即ICln和SMN复合体（SMN/Gemin2/Gemin6 - 8）。在此，我们使用重组蛋白重构伴侣机制，并系统地研究了这些蛋白的作用。我们发现，与人类系统一样，（某种生物）中的组装过程依次需要ICln和SMN复合体。然而，存在一些显著差异。例如，h_F/E/G形成异源六聚体和异源三聚体，而Sp_F/E/G仅形成异源六聚体；单独的h_Gemin2可以结合D1/D2/F/E/G，但Sp_Gemin2不能。此外，我们通过遗传学方法发现Sp_Gemin2是必不可少的。这些机制研究表明，这六种蛋白在分子水平上对于Sm核心组装是必要且充分的，并丰富了我们对物种变异和进化中伴侣系统的理解。
