Stabilisation of half MCM ring by Cdt1 during DNA insertion

Nat Commun. 2021 Mar 19;12(1):1746. doi: 10.1038/s41467-021-21932-8.


Origin licensing ensures precise once per cell cycle replication in eukaryotic cells. The Origin Recognition Complex, Cdc6 and Cdt1 load Mcm2-7 helicase (MCM) into a double hexamer, bound around duplex DNA. The complex formed by ORC-Cdc6 bound to duplex DNA (OC) recruits the MCM-Cdt1 complex into the replication origins. Through the stacking of both complexes, the duplex DNA is inserted inside the helicase by an unknown mechanism. In this paper we show that the DNA insertion comes with a topological problem in the stacking of OC with MCM-Cdt1. Unless an essential, conserved C terminal winged helix domain (C-WHD) of Cdt1 is present, the MCM splits into two halves. The binding of this domain with the essential C-WHD of Mcm6, allows the latching between the MCM-Cdt1 and OC, through a conserved Orc5 AAA-lid interaction. Our work provides new insights into how DNA is inserted into the eukaryotic replicative helicase, through a series of synchronized events.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Cycle Proteins / chemistry
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • DNA Replication / physiology*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Minichromosome Maintenance Complex Component 6 / chemistry
  • Minichromosome Maintenance Complex Component 6 / metabolism
  • Minichromosome Maintenance Proteins / chemistry
  • Minichromosome Maintenance Proteins / genetics
  • Minichromosome Maintenance Proteins / metabolism*
  • Nuclear Proteins / metabolism
  • Origin Recognition Complex / chemistry
  • Origin Recognition Complex / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*


  • CDC6 protein, S cerevisiae
  • Cell Cycle Proteins
  • DNA-Binding Proteins
  • Nuclear Proteins
  • ORC4 protein, S cerevisiae
  • ORC5 protein, S cerevisiae
  • Origin Recognition Complex
  • Saccharomyces cerevisiae Proteins
  • TAH11 protein, S cerevisiae
  • MCM6 protein, S cerevisiae
  • Minichromosome Maintenance Complex Component 6
  • Minichromosome Maintenance Proteins