DNA binding polarity, dimerization, and ATPase ring remodeling in the CMG helicase of the eukaryotic replisome
- London Research Institute, Cancer Research UK, United Kingdom
- University of California, Berkeley, United States
- University of California, Berkeley, United Kingdom
- University of Tartu, Estonia
- National Institute for Biological Standards and Control, United Kingdom
- King's College London, United Kingdom
- Johns Hopkins University School of Medicine, United States
Abstract
The Cdc45/Mcm2-7/GINS (CMG) helicase separates DNA strands during replication in eukaryotes. How the CMG is assembled and engages DNA substrates remains unclear. We have determined the electron-microscopy structure of the CMG in the presence of ATPγS and a DNA duplex bearing a 3' single-stranded tail. The structure shows that the MCM subunits of the CMG bind preferentially to single-stranded DNA, establishes the polarity by which DNA enters into the Mcm2-7 pore, and explains how Cdc45 helps prevent DNA from dissociating from the helicase. The Mcm2-7 subcomplex forms a cracked-ring, right-handed spiral when DNA and nucleotide are bound, revealing unexpected congruencies between the CMG and both bacterial DnaB helicases and the AAA+ motor of the eukaryotic proteasome. The existence of a subpopulation of dimeric CMGs establishes the subunit register of Mcm2-7 double hexamers and highlights how Mcm2-7 transitions through different conformational and assembly states as it matures into a functional helicase.
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© 2014, Costa 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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DNA binding polarity, dimerization, and ATPase ring remodeling in the CMG helicase of the eukaryotic replisome
eLife 3:e03273.
https://doi.org/10.7554/eLife.03273
