Mechanism of assembly of snRNP cores assisted by ICln and the SMN complex in fission yeast

Yan Hu; Yan Hou; Shijie Zhou; Yingzhi Wang; Congcong Shen; Li Mu; Dan Su; Rundong Zhang

doi:10.1016/j.isci.2023.107604

Mechanism of assembly of snRNP cores assisted by ICln and the SMN complex in fission yeast

iScience. 2023 Aug 12;26(9):107604. doi: 10.1016/j.isci.2023.107604. eCollection 2023 Sep 15.

Authors

Yan Hu^{1

2}, Yan Hou^{1

2}, Shijie Zhou^{1

2}, Yingzhi Wang^{1

2}, Congcong Shen^{1

2}, Li Mu^{1

2}, Dan Su², Rundong Zhang^{1

2}

Affiliations

¹ Department of Ophthalmology, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu 610041, P.R. China.
² State Key Laboratory of Biotherapy, West China Hospital, Sichuan University and Collaborative Innovation Center for Biotherapy, Chengdu 610041, P.R. China.

Abstract

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 Schizosaccharomyces pombe (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 S. pombe 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.

Keywords: Experimental systems for structural biology; Model organism; Molecular genetics; Molecular interaction; Protein.