title: Cryo-EM structures of the eukaryotic replicative helicase bound to a translocation substrate.
abstract: The Cdc45-MCM-GINS (CMG) helicase unwinds DNA during the elongation step of eukaryotic genome duplication and this process depends on the MCM ATPase function. Whether CMG translocation occurs on single- or double-stranded DNA and how ATP hydrolysis drives DNA unwinding remain open questions. Here we use cryo-electron microscopy to describe two subnanometre resolution structures of the CMG helicase trapped on a DNA fork. In the predominant state, the ring-shaped C-terminal ATPase of MCM is compact and contacts single-stranded DNA, via a set of pre-sensor 1 hairpins that spiral around the translocation substrate. In the second state, the ATPase module is relaxed and apparently substrate free, while DNA intimately contacts the downstream amino-terminal tier of the MCM motor ring. These results, supported by single-molecule FRET measurements, lead us to suggest a replication fork unwinding mechanism whereby the N-terminal and AAA+ tiers of the MCM work in concert to translocate on single-stranded DNA.
authors.affiliation: Macromolecular Machines, Clare Hall Laboratory, The Francis Crick Institute, Blanche Lane, South Mimms EN6 3LD, UK.
authors.forename: Ferdos
authors.initials: F
authors.lastname: Abid Ali
authors.affiliation: Macromolecular Machines, Clare Hall Laboratory, The Francis Crick Institute, Blanche Lane, South Mimms EN6 3LD, UK.|National Institute for Biological Standards and Control, Microscopy and Imaging, Blanche Lane, South Mimms EN6 3QG, UK.
authors.forename: Ludovic
authors.identifier: http://orcid.org/0000-0001-6464-8808
authors.initials: L
authors.lastname: Renault
authors.affiliation: Macromolecular Machines, Clare Hall Laboratory, The Francis Crick Institute, Blanche Lane, South Mimms EN6 3LD, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: Gannon
authors.affiliation: Section of Virology and Single Molecule Imaging Group, Department of Medicine, MRC Clinical Centre, Imperial College London, London W12 0NN, UK.
authors.forename: Hailey L
authors.initials: HL
authors.lastname: Gahlon
authors.affiliation: Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
authors.forename: Abhay
authors.identifier: http://orcid.org/0000-0002-4480-5439
authors.initials: A
authors.lastname: Kotecha
authors.affiliation: Macromolecular Machines, Clare Hall Laboratory, The Francis Crick Institute, Blanche Lane, South Mimms EN6 3LD, UK.
authors.forename: Jin Chuan
authors.initials: JC
authors.lastname: Zhou
authors.affiliation: Section of Virology and Single Molecule Imaging Group, Department of Medicine, MRC Clinical Centre, Imperial College London, London W12 0NN, UK.
authors.forename: David
authors.identifier: http://orcid.org/0000-0003-4657-6323
authors.initials: D
authors.lastname: Rueda
authors.affiliation: Macromolecular Machines, Clare Hall Laboratory, The Francis Crick Institute, Blanche Lane, South Mimms EN6 3LD, UK.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Costa
mesh_terms: D020285:Cryoelectron Microscopy; D004247:DNA / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004265:DNA Helicases / Q000378:metabolism* / Q000648:ultrastructure; D004261:DNA Replication; D056890:Eukaryota / Q000201:enzymology* / Q000235:genetics / Q000648:ultrastructure
chemical_list: D004247:DNA; D004265:DNA Helicases