CMG helicase disassembly is controlled by replication fork DNA, replisome components and a ubiquitin threshold

Abstract

The eukaryotic replisome assembles around the CMG helicase, which stably associates with DNA replication forks throughout elongation. When replication terminates, CMG is ubiquitylated on its Mcm7 subunit and disassembled by the Cdc48 / p97 ATPase. Until now, the regulation that restricts CMG ubiquitylation to termination was unknown, as was the mechanism of disassembly. By reconstituting these processes with purified budding yeast proteins, we show that ubiquitylation is tightly repressed throughout elongation by the Y-shaped DNA structure of replication forks. Termination removes the repressive DNA structure, whereupon long K48-linked ubiquitin chains are conjugated to CMG-Mcm7, dependent on multiple replisome components that bind to the ubiquitin ligase SCFDia2. This mechanism pushes CMG beyond a '5-ubiquitin threshold' that is inherent to Cdc48, which specifically unfolds ubiquitylated Mcm7 and thereby disassembles CMG. These findings explain the exquisite regulation of CMG disassembly and provide a general model for the disassembly of ubiquitylated protein complexes by Cdc48.

Data availability

All data generated or analysed during this study are included in the manuscript and supporting files.

Article and author information

Author details

  1. Tom D Deegan

    MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, United Kingdom
    For correspondence
    tdeegan@dundee.ac.uk
    Competing interests
    The authors declare that no competing interests exist.
  2. Pragya P Mukherjee

    MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  3. Ryo Fujisawa

    MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  4. Cristian Polo Rivera

    MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, United Kingdom
    Competing interests
    The authors declare that no competing interests exist.
  5. Karim Labib

    MRC Protein Phosphorylation and Ubiquitylation Unit, University of Dundee, Dundee, United Kingdom
    For correspondence
    kpmlabib@dundee.ac.uk
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-8861-379X

Funding

Medical Research Council (MC_UU_12016/13)

  • Tom D Deegan
  • Pragya P Mukherjee
  • Ryo Fujisawa
  • Cristian Polo Rivera
  • Karim Labib

Wellcome (102943/Z/13/Z)

  • Karim Labib

Wellcome (204678/Z/16/Z)

  • Tom D Deegan

Cancer Research UK (C578/A24558)

  • Ryo Fujisawa
  • Karim Labib

Cancer Research UK (C578/A25669)

  • Cristian Polo Rivera
  • Karim Labib

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Bruce Stillman, Cold Spring Harbor Laboratory, United States

Version history

  1. Received: June 24, 2020
  2. Accepted: August 14, 2020
  3. Accepted Manuscript published: August 17, 2020 (version 1)
  4. Version of Record published: September 1, 2020 (version 2)

Copyright

© 2020, Deegan 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. Tom D Deegan
  2. Pragya P Mukherjee
  3. Ryo Fujisawa
  4. Cristian Polo Rivera
  5. Karim Labib
(2020)
CMG helicase disassembly is controlled by replication fork DNA, replisome components and a ubiquitin threshold
eLife 9:e60371.
https://doi.org/10.7554/eLife.60371

Share this article

https://doi.org/10.7554/eLife.60371

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