Molecular architecture of the 90S small subunit pre-ribosome
- School of Life Sciences, Tsinghua University, China
- Chinese Academy of Sciences, China
- National Institute of Biological Sciences, China
Abstract
Eukaryotic small ribosomal subunits are first assembled into 90S pre-ribosomes. The complete 90S is a gigantic complex with a molecular mass of approximately 5 megadaltons. Here, we report the nearly complete architecture of Saccharomyces cerevisiae 90S determined from three cryo-electron microscopy single particle reconstructions at 4.5 to 8.7 angstrom resolution. Majority of the density maps were modeled and assigned to specific RNA and protein components. The nascent ribosome is assembled into isolated native-like substructures that are stabilized by abundant assembly factors. The 5' external transcribed spacer and U3 snoRNA nucleate a large subcomplex that scaffolds the nascent ribosome. U3 binds four sites of pre-rRNA, including a novel site on helix 27 but not the 3' side of the central pseudoknot, and crucially organizes the 90S structure. The 90S model provides significant insight into the principle of small subunit assembly and the function of assembly factors.
Article and author information
Author details
Funding
National Natural Science Foundation of China (91540201; 31430024; 31325007)
- Keqiong Ye
Chinese Academy of Sciences (XDB08010203)
- Keqiong Ye
Ministry of Science and Technology of the People's Republic of China (2014CB84980001)
- Meng-Qiu Dong
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Reviewing Editor
- Alan G Hinnebusch, National Institutes of Health, United States
Version history
- Received: October 7, 2016
- Accepted: February 26, 2017
- Accepted Manuscript published: February 28, 2017 (version 1)
- Version of Record published: March 16, 2017 (version 2)
- Version of Record updated: June 26, 2017 (version 3)
Copyright
© 2017, Sun et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Molecular architecture of the 90S small subunit pre-ribosome
eLife 6:e22086.
https://doi.org/10.7554/eLife.22086
Further reading
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- Cell Biology
- Structural Biology and Molecular Biophysics
Mutations in the human PURA gene cause the neurodevelopmental PURA syndrome. In contrast to several other monogenetic disorders, almost all reported mutations in this nucleic acid-binding protein result in the full disease penetrance. In this study, we observed that patient mutations across PURA impair its previously reported co-localization with processing bodies. These mutations either destroyed the folding integrity, RNA binding, or dimerization of PURA. We also solved the crystal structures of the N- and C-terminal PUR domains of human PURA and combined them with molecular dynamics simulations and nuclear magnetic resonance measurements. The observed unusually high dynamics and structural promiscuity of PURA indicated that this protein is particularly susceptible to mutations impairing its structural integrity. It offers an explanation why even conservative mutations across PURA result in the full penetrance of symptoms in patients with PURA syndrome.
