Excess Mcm2-7 License Dormant Origins of Replication That Can Be Used Under Conditions of Replicative Stress

J Cell Biol. 2006 Jun 5;173(5):673-83. doi: 10.1083/jcb.200602108.

Abstract

In late mitosis and early G1, replication origins are licensed for subsequent use by loading complexes of the minichromosome maintenance proteins 2-7 (Mcm2-7). The number of Mcm2-7 complexes loaded onto DNA greatly exceeds the number of replication origins used during S phase, but the function of the excess Mcm2-7 is unknown. Using Xenopus laevis egg extracts, we show that these excess Mcm2-7 complexes license additional dormant origins that do not fire during unperturbed S phases because of suppression by a caffeine-sensitive checkpoint pathway. Use of these additional origins can allow complete genome replication in the presence of replication inhibitors. These results suggest that metazoan replication origins are actually comprised of several candidate origins, most of which normally remain dormant unless cells experience replicative stress. Consistent with this model, using Caenorhabditis elegans, we show that partial RNAi-based knockdown of MCMs that has no observable effect under normal conditions causes lethality upon treatment with low, otherwise nontoxic, levels of the replication inhibitor hydroxyurea.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / drug effects
  • Adenosine Triphosphatases / metabolism
  • Animals
  • Aphidicolin / pharmacology
  • Caenorhabditis elegans / drug effects
  • Caenorhabditis elegans / growth & development
  • Caffeine / pharmacology
  • Carrier Proteins / drug effects
  • Carrier Proteins / metabolism
  • Cell Cycle Proteins / drug effects
  • Cell Cycle Proteins / metabolism
  • Cell Survival / drug effects
  • Chromatin / drug effects
  • Chromatin / metabolism
  • DNA Replication / drug effects
  • DNA Replication / physiology*
  • DNA-Binding Proteins / drug effects
  • DNA-Binding Proteins / metabolism
  • Hydroxyurea / pharmacology
  • Minichromosome Maintenance Complex Component 2
  • Minichromosome Maintenance Complex Component 3
  • Minichromosome Maintenance Complex Component 4
  • Minichromosome Maintenance Complex Component 7
  • Nuclear Proteins / drug effects
  • Nuclear Proteins / metabolism
  • Oxidative Stress / physiology*
  • Replication Origin*
  • Time Factors
  • Xenopus Proteins / drug effects
  • Xenopus Proteins / metabolism*
  • Xenopus laevis

Substances

  • Carrier Proteins
  • Cell Cycle Proteins
  • Chromatin
  • DNA-Binding Proteins
  • Nuclear Proteins
  • Xenopus Proteins
  • mcm5 protein, Xenopus
  • mcm6a protein, Xenopus
  • Aphidicolin
  • Caffeine
  • Adenosine Triphosphatases
  • MCM3 protein, Xenopus
  • MCM4 protein, human
  • Mcm2 protein, Xenopus
  • Mcm7 protein, Xenopus
  • Minichromosome Maintenance Complex Component 2
  • Minichromosome Maintenance Complex Component 3
  • Minichromosome Maintenance Complex Component 4
  • Minichromosome Maintenance Complex Component 7
  • Hydroxyurea