View the Current Issue

Article

  • The EMBO Journal (2008) 27, 758 - 769
  • doi:10.1038/emboj.2008.16

Published online: 7 February 2008

Cdk1 and Cdk2 activity levels determine the efficiency of replication origin firing in Xenopus

Liliana Krasinska1,4, Emilie Besnard2,4, Emilie Cot1,4, Christiane Dohet1,4, Marcel Méchali3, Jean-Marc Lemaitre2,4 and Daniel Fisher1,4

  1. Laboratory of Phosphorylation and Cell Cycle Control, Institut de Génétique Moléculaire de Montpellier, CNRS, UMR5535, Montpellier, France
  2. Institut de Génomique Fonctionnelle, CNRS, UMR5203, Inserm, U661, Université de Montpellier I et II, Montpellier, France
  3. Institut de Génétique Humaine, CNRS, UPR1142, Montpellier, France
  4. Inserm, Equipe Avenir, Montpellier, France

Correspondence to:

Daniel Fisher, Laboratory of Phosphorylation and Cell Cycle Control, CNRS, UMR 5535—Institut de Génétique Moléculaire, 1919 Route de Mende, Montpellier cedex 5 34293, France. Tel.: +33 467 61 36 94; Fax: +33 467 04 02 31; E-mail: fisher@igmm.cnrs.fr

Received 3 September 2007; Accepted 18 January 2008

In this paper, we describe how, in a model embryonic system, cyclin-dependent kinase (Cdk) activity controls the efficiency of DNA replication by determining the frequency of origin activation. Using independent approaches of protein depletion and selective chemical inhibition of a single Cdk, we find that both Cdk1 and Cdk2 are necessary for efficient DNA replication in Xenopus egg extracts. Eliminating Cdk1, Cdk2 or their associated cyclins changes replication origin spacing, mainly by decreasing frequency of activation of origin clusters. Although there is no absolute requirement for a specific Cdk or cyclin, Cdk2 and cyclin E contribute more to origin cluster efficiency than Cdk1 and cyclin A. Relative Cdk activity required for DNA replication is very low, and even when both Cdk1 and Cdk2 are strongly inhibited, some origins are activated. However, at low levels, Cdk activity is limiting for the pre-replication complex to pre-initiation complex transition, origin activation and replication efficiency. As such, unlike mitosis, initiation of DNA replication responds progressively to changes in Cdk activity at low activity levels.

  • Keywords:

    • CDK,
    • DNA replication,
    • replication origin