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Visualizing the Assembly Pathway of Nucleolar Pre-60S Ribosomes
Lukas Kater1, Matthias Thoms2, Clara Barrio-Garcia1
1Gene Center Munich and Center of Integrated Protein Science-Munich (CiPS-M), Department of Biochemistry, Feodor-Lynen-Str. 25, University of Munich, 81377 Munich, Germany.
Cell
|December 16, 2017
Summary
This study reveals the early steps of eukaryotic 60S ribosomal subunit assembly in the nucleolus using cryo-electron microscopy. It details the structural pathway and identifies key protein complexes involved in ribosome biogenesis.
Area of Science:
- Molecular Biology
- Structural Biology
- Cell Biology
Background:
- Eukaryotic 60S ribosomal subunit biogenesis is a complex process occurring in the nucleolus.
- Limited structural data exists for early assembly intermediates, hindering understanding of this crucial pathway.
Purpose of the Study:
- To elucidate the structural pathway of early 60S ribosomal subunit assembly.
- To identify and map the roles of assembly factors in ribosome biogenesis.
Main Methods:
- Cryo-electron microscopy (cryo-EM) was employed to determine structures of early 60S biogenesis intermediates.
- High-resolution structures were obtained ranging from 3.3 Å to 4.5 Å.
Main Results:
- Distinct immature rRNA conformations and 25 assembly factors in six states were identified.
- The Nsa1-Rrp1-Rpf1-Mak16 module stabilizes the subunit's solvent side.
- The Erb1-Ytm1-Nop7 complex organizes multiple factors and rRNA domains.
Conclusions:
- Structural snapshots reveal the stepwise integration and compaction of major 60S domains.
- Assembly progresses from the solvent side around the exit tunnel towards the central protuberance.
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