Abstract

Within a single generation time a growing yeast cell imports ~14 million ribosomal proteins (r-proteins) into the nucleus for ribosome production. After import, it is unclear how these intrinsically unstable and aggregation-prone proteins are targeted to the ribosome assembly site in the nucleolus. Here, we report the discovery of a conserved nuclear carrier Tsr2 that coordinates transfer of the r-protein eS26 to the earliest assembling pre-ribosome, the 90S. In vitro studies revealed that Tsr2 efficiently dissociates importin:eS26 complexes via an atypical RanGTP-independent mechanism that terminates the import process. Subsequently, Tsr2 binds the released eS26, shields it from proteolysis, and ensures its safe delivery to the 90S pre-ribosome. We anticipate similar carriers - termed here escortins - to securely connect the nuclear import machinery with pathways that deposit r-proteins onto developing pre-ribosomal particles.

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  1. Sabina Schütz

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  2. Ute Fischer

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  3. Martin Altvater

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  4. Purnima Nerurkar

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  5. Cohue Peña

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  6. Michaela Gerber

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  7. Yiming Chang

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  8. Stefanie Caesar

    Universität des Saarlandes, Homburg, Germany
    Competing interests
    The authors declare that no competing interests exist.
  9. Olga T Schubert

    ETH Zürich, Zürich, Switzerland
    Competing interests
    The authors declare that no competing interests exist.
  10. Gabriel Schlenstedt

    Universität des Saarlandes, Homburg, Germany
    Competing interests
    The authors declare that no competing interests exist.
  11. Vikram G Panse

    ETH Zürich, Zürich, Switzerland
    For correspondence
    vikram.panse@bc.biol.ethz.ch
    Competing interests
    The authors declare that no competing interests exist.

Copyright

© 2014, Schütz 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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  1. Sabina Schütz
  2. Ute Fischer
  3. Martin Altvater
  4. Purnima Nerurkar
  5. Cohue Peña
  6. Michaela Gerber
  7. Yiming Chang
  8. Stefanie Caesar
  9. Olga T Schubert
  10. Gabriel Schlenstedt
  11. Vikram G Panse
(2014)
A RanGTP-independent mechanism allows ribosomal protein nuclear import for ribosome assembly
eLife 3:e03473.
https://doi.org/10.7554/eLife.03473

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https://doi.org/10.7554/eLife.03473

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