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  • The EMBO Journal (2006) 25, 346 - 356
  • doi:10.1038/sj.emboj.7600927

Published online: 5 January 2006

DnaA couples DNA replication and the expression of two cell cycle master regulators

Justine Collier, Sean Richard Murray and Lucy Shapiro

  1. Department of Developmental Biology, School of Medicine, Stanford University Medical Center, Beckman Center, Stanford, CA, USA

Correspondence to:

Lucy Shapiro, Department of Developmental Biology, School of Medicine, Stanford University Medical Center, Beckman Center, Stanford B351, CA 94305, USA. Tel.: +1 650 725 7678; Fax: +1 650 725 7739; E-mail: shapiro@stanford.edu

Received 12 August 2005; Accepted 28 November 2005

Cell cycle progression in Caulobacter is driven by the master transcriptional regulators CtrA and GcrA. The cellular levels of CtrA and GcrA are temporally and spatially out-of-phase during the cell cycle, with CtrA repressing gcrA transcription and GcrA activating ctrA transcription. Here, we show that DnaA, a protein required for the initiation of DNA replication, also functions as a transcriptional activator of gcrA, which in turn activates multiple genes, notably those involved in chromosome replication and segregation. The cellular concentration of DnaA is cell cycle-controlled, peaking at the time of replication initiation and gcrA induction. Regulated proteolysis of GcrA contributes to the cell cycle variations in GcrA abundance. We propose that DnaA couples DNA replication initiation with the expression of the two oscillating regulators GcrA and CtrA and that the DnaA/GcrA/CtrA regulatory cascade drives the forward progression of the Caulobacter cell cycle.

  • Keywords:

    • Caulobacter crescentus,
    • CtrA,
    • DnaA,
    • GcrA,
    • proteolysis