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Modular assembly of the nucleolar pre-60S ribosomal subunit



Early co-transcriptional events of eukaryotic ribosome assembly result in the formation of precursors of the small (40S) and large (60S) ribosomal subunits1. A multitude of transient assembly factors regulate and chaperone the systematic folding of pre-ribosomal RNA subdomains. However, due to limited structural information, the role of these factors during early nucleolar 60S assembly is not fully understood. Here we have determined cryo-EM reconstructions of the nucleolar pre-60S ribosomal subunit in different conformational states at resolutions up to 3.4 Å. These reconstructions reveal how steric hindrance and molecular mimicry are used to prevent both premature folding states and binding of later factors. This is accomplished by the concerted activity of 21 ribosome assembly factors that stabilize and remodel pre-ribosomal RNA and ribosomal proteins. Among these factors, three Brix-domain proteins and their binding partners form a ring-like structure at rRNA domain boundaries to support the architecture of the maturing particle. Mutually exclusive conformations of these pre-60S particles suggest that the formation of the polypeptide exit tunnel is achieved through different folding pathways during subsequent stages of ribosome assembly. These structures rationalize previous genetic and biochemical data and highlight the mechanisms driving eukaryotic ribosome assembly in a unidirectional manner.

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Author information

Author notes

    • Zahra Assur Sanghai
    •  & Linamarie Miller

    equal contribution


  1. Laboratory of Protein and Nucleic Acid Chemistry, The Rockefeller University, New York, New York 10065, USA

    • Zahra Assur Sanghai
    • , Linamarie Miller
    • , Jonas Barandun
    • , Mirjam Hunziker
    • , Malik Chaker-Margot
    •  & Sebastian Klinge
  2. Tri-Institutional Training Program in Chemical Biology, The Rockefeller University, New York, New York 10065, USA

    • Linamarie Miller
    •  & Malik Chaker-Margot
  3. Laboratory of Mass Spectrometry and Gaseous Ion Chemistry, The Rockefeller University, New York, New York 10065, USA

    • Kelly R. Molloy
    • , Junjie Wang
    •  & Brian T. Chait


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Corresponding author

Correspondence to Sebastian Klinge.

Supplementary information

PDF files

  1. 1.

    Life Sciences Reporting Summary

  2. 2.

    Supplementary Figure 1

    Source data for the RNA gel and northern blots showing the uncropped images for Extended Data Figure 1d and e.

CSV files

  1. 1.

    Supplementary Data 1

    DSS cross-links for the nucleolar pre-60S ribosomal subunit.

Zip files

  1. 1.

    Supplementary Data 2

    PyMOL session file for the structural analysis of the nucleolar pre-60S ribosomal subunit.


  1. 1.

    360° view of the cryo-EM reconstruction of the S. cerevisiae nucleolar pre-60S particle

    A 360° rotation of a composite cryo-EM map consisting of the 3.4 Å state 1 and the 3.7 Å state 2 maps. Densities for nucleolar pre-60S assembly factors and rRNA domains are colour-coded as in Figure 1 and ribosomal proteins are colored in grey. The rotation is paused at front and back view as shown in Figure 1.


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