1. Biochemistry and Chemical Biology
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Action of CMG with strand-specific DNA blocks supports an internal unwinding mode for the eukaryotic replicative helicase

  1. Lance D Langston
  2. Mike E O'Donnell  Is a corresponding author
  1. Howard Hughes Medical Institute, The Rockefeller University, United States
Research Article
  • Cited 24
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Cite this article as: eLife 2017;6:e23449 doi: 10.7554/eLife.23449

Abstract

Replicative helicases are ring-shaped hexamers that encircle DNA for duplex unwinding. The currently accepted view of hexameric helicase function is by steric exclusion, where the helicase encircles one DNA strand and excludes the other, acting as a wedge with an external DNA unwinding point during translocation. Accordingly, strand specific blocks only affect these helicases when placed on the tracking strand, not the excluded strand. We examined the effect of blocks on the eukaryotic CMG and, contrary to expectations, blocks on either strand inhibit CMG unwinding. A recent cryoEM structure of yeast CMG shows that duplex DNA enters the helicase and unwinding occurs in the central channel. The results of this report inform important aspects of the structure and we propose that CMG functions by a modified steric exclusion process in which both strands enter the helicase and the duplex unwinding point is internal, followed by exclusion of the non-tracking strand.

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Author details

  1. Lance D Langston

    Howard Hughes Medical Institute, The Rockefeller University, New York City, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-2736-9284
  2. Mike E O'Donnell

    Howard Hughes Medical Institute, The Rockefeller University, New York City, United States
    For correspondence
    odonnel@mail.rockefeller.edu
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0001-9002-4214

Funding

Howard Hughes Medical Institute

  • Lance D Langston
  • Mike E O'Donnell

National Institutes of Health (GM38839)

  • Mike E O'Donnell

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

Reviewing Editor

  1. Stephen C Kowalczykowski, University of California, Davis, United States

Publication history

  1. Received: November 19, 2016
  2. Accepted: March 23, 2017
  3. Accepted Manuscript published: March 27, 2017 (version 1)
  4. Version of Record published: April 5, 2017 (version 2)

Copyright

© 2017, Langston & O'Donnell

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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