Mechanism and timing of Mcm2-7 ring closure during DNA replication origin licensing

Nat Struct Mol Biol. 2017 Mar;24(3):309-315. doi: 10.1038/nsmb.3375. Epub 2017 Feb 13.


The opening and closing of two ring-shaped Mcm2-7 DNA helicases is necessary to license eukaryotic origins of replication, although the mechanisms controlling these events are unclear. The origin-recognition complex (ORC), Cdc6 and Cdt1 facilitate this process by establishing a topological link between each Mcm2-7 hexamer and origin DNA. Using colocalization single-molecule spectroscopy and single-molecule Förster resonance energy transfer (FRET), we monitored ring opening and closing of Saccharomyces cerevisiae Mcm2-7 during origin licensing. The two Mcm2-7 rings were open during initial DNA association and closed sequentially, concomitant with the release of their associated Cdt1. We observed that ATP hydrolysis by Mcm2-7 was coupled to ring closure and Cdt1 release, and failure to load the first Mcm2-7 prevented recruitment of the second Mcm2-7. Our findings identify key mechanisms controlling the Mcm2-7 DNA-entry gate during origin licensing, and reveal that the two Mcm2-7 complexes are loaded via a coordinated series of events with implications for bidirectional replication initiation and quality control.

MeSH terms

  • Adenosine Triphosphate / metabolism
  • DNA Replication*
  • DNA, Fungal / metabolism
  • Hydrolysis
  • Minichromosome Maintenance Proteins / chemistry*
  • Minichromosome Maintenance Proteins / metabolism*
  • Models, Biological
  • Protein Conformation
  • Protein Multimerization
  • Replication Origin*
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / metabolism
  • Time Factors


  • DNA, Fungal
  • Saccharomyces cerevisiae Proteins
  • Adenosine Triphosphate
  • Minichromosome Maintenance Proteins