Volume 28, No 12, Dec 2018

ISSN: 1001-0602 
EISSN: 1748-7838 2018 
impact factor 17.848* 
(Clarivate Analytics, 2019)

Volume 28 Issue 12, December 2018: 1129-1140

ORIGINAL ARTICLES

Structures of the human pre-catalytic spliceosome and its precursor spliceosome

Xiechao Zhan ¹, Chuangye Yan ¹, Xiaofeng Zhang ¹, Jianlin Lei ^1,2 and Yigong Shi ^1,3

¹Beijing Advanced Innovation Center for Structural Biology, Tsinghua-Peking Joint Center for Life Sciences, School of Life Sciences and School of Medicine, Tsinghua University,Beijing 100084, China; ² Technology Center for Protein Sciences, Ministry of Education Key Laboratory of Protein Sciences, School of Life Sciences, Tsinghua University, Beijing 100084, China and ³Institute of Biology, Westlake Institute for Advanced Study, Westlake University, 18 Shilongshan Road, Xihu District, Hangzhou, Zhejiang 310024, China Correspondence: Correspondence: Chuangye Yan (yancy@mails.tsinghua.edu.cn) or Yigong Shi (shi-lab@tsinghua.edu.cn)These authors contributed equally: Xiechao Zhan, Chuangye Yan, Xiaofeng Zhang

The pre-catalytic spliceosome (B complex) is preceded by its precursor spliceosome (pre-B complex) and followed by the activated spliceosome (Bact complex). The pre-B-to-B and B-to-Bact transitions are driven by the ATPase/helicases Prp28 and Brr2, respectively. In this study, we report the cryo-electron microscopy structures of the human pre-B complex and the human B complex at an average resolution of 5.7 and 3.8 Å, respectively. In the pre-B complex, U1 and U2 small nuclear ribonucleoproteins (snRNPs) associate with two edges of the tetrahedron-shaped U4/U6.U5 tri-snRNP. The pre-mRNA is yet to be recognized by U5 or U6 small nuclear RNA (snRNA), and loop I of U5 snRNA remains unengaged. In the B complex, U1 snRNP and Prp28 are dissociated, the 5’-exon is anchored to loop I of U5 snRNA, and the 5′-splice site is recognized by U6 snRNA through duplex formation. In sharp contrast to S. cerevisiae, most components of U2 snRNP and tri-snRNP, exemplified by Brr2, undergo pronounced rearrangements in the human pre-B-to-B transition. Structural analysis reveals mechanistic insights into the assembly and activation of the human spliceosome.

https://doi.org/10.1038/s41422-018-0094-7

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