Molecular basis for ATP-hydrolysis-driven DNA translocation by the CMG helicase of the eukaryotic replisome
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Patrik Eickhoff Hazal Kose Fabrizio Martino Tatjana Petojevic Ferdos Abid Ali Julia Locke Nele Tamberg Andrea Nans James M Berger Michael R Botchan Hasan Yardimci Alessandro CostaAbstract
In the eukaryotic replisome, DNA unwinding by the Cdc45-MCM-Go-Ichi-Ni-San (GINS) (CMG) helicase requires a hexameric ring-shaped ATPase named minichromosome maintenance (MCM), which spools single-stranded DNA through its central channel. Not all six ATPase sites are required for unwinding; however, the helicase mechanism is unknown. We imaged ATP-hydrolysis-driven translocation of the CMG using cryo-electron microscopy (cryo-EM) and found that the six MCM subunits engage DNA using four neighboring protomers at a time, with ATP binding promoting DNA engagement. Morphing between different helicase states leads us to suggest a non-symmetric hand-over-hand rotary mechanism, explaining the asymmetric requirements of ATPase function around the MCM ring of the CMG. By imaging of a higher-order replisome assembly, we find that the Mrc1-Csm3-Tof1 fork-stabilization complex strengthens the interaction between parental duplex DNA and the CMG at the fork, which might support the coupling between DNA translocation and fork unwinding.
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Publisher website (DOI) 10.1016/j.celrep.2019.07.104
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Europe PubMed Central 31484077
Pubmed 31484077
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