1. Chromosomes and Gene Expression
  2. Physics of Living Systems
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Chromosome organization by one-sided and two-sided loop extrusion

  1. Edward J Banigan
  2. Aafke A van den Berg
  3. Hugo B Brandão
  4. John F Marko
  5. Leonid A Mirny  Is a corresponding author
  1. Massachusetts Institute of Technology, United States
  2. Harvard University, United States
  3. Northwestern University, United States
Research Article
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Cite this article as: eLife 2020;9:e53558 doi: 10.7554/eLife.53558

Abstract

SMC complexes, such as condensin or cohesin, organize chromatin throughout the cell cycle by a process known as loop extrusion. SMC complexes reel in DNA, extruding and progressively growing DNA loops. Modeling assuming two-sided loop extrusion reproduces key features of chromatin organization across different organisms. In vitro single-molecule experiments confirmed that yeast condensins extrude loops, however, they remain anchored to their loading sites and extrude loops in a 'one-sided' manner. We therefore simulate one-sided loop extrusion to investigate whether 'one-sided' complexes can compact mitotic chromosomes, organize interphase domains, and juxtapose bacterial chromosomal arms, as can be done by 'two-sided' loop extruders. While one-sided loop extrusion cannot reproduce these phenomena, variants can recapitulate in vivo observations. We predict that SMC complexes in vivo constitute effectively two-sided motors or exhibit biased loading and propose relevant experiments. Our work suggests that loop extrusion is a viable general mechanism of chromatin organization.

Article and author information

Author details

  1. Edward J Banigan

    Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5478-7425
  2. Aafke A van den Berg

    Department of Physics and Institute for Medical Engineering & Science, Massachusetts Institute of Technology, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
  3. Hugo B Brandão

    Graduate Program in Biophysics, Harvard University, Cambridge, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-5496-0638
  4. John F Marko

    Department of Molecular Biosciences, Department of Physics and Astronomy, Northwestern University, Evanston, United States
    Competing interests
    The authors declare that no competing interests exist.
  5. Leonid A Mirny

    Institute for Medical Engineering and Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, United States
    For correspondence
    lmirny@gmail.com
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-0785-5410

Funding

National Institutes of Health (U54DK107980)

  • Edward J Banigan
  • Aafke A van den Berg
  • Hugo B Brandão
  • John F Marko
  • Leonid A Mirny

National Institutes of Health (U54CA193419)

  • Edward J Banigan
  • Aafke A van den Berg
  • Hugo B Brandão
  • John F Marko
  • Leonid A Mirny

National Institutes of Health (GM114190)

  • Edward J Banigan
  • Aafke A van den Berg
  • Hugo B Brandão
  • Leonid A Mirny

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

Reviewing Editor

  1. Kevin Struhl, Harvard Medical School, United States

Publication history

  1. Received: November 13, 2019
  2. Accepted: April 3, 2020
  3. Accepted Manuscript published: April 6, 2020 (version 1)

Copyright

© 2020, Banigan 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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