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

Abstract

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.

The dynamic interplay between a cell fate determinant and a lysozyme homolog drives the asymmetric division cycle of Caulobacter crescentus

“…The regulatory pathways controlling DivK are central for the G1-S transition and likely act in concert with others to complete the underlying developmental changes that remodel a swarmer cell into a replicative stalked cell. These include pathways specified by the master transcriptional regulators GcrA and DnaA as well as the SsrA (tmRNA) quality control system, all of which are active during the G1-S transition and facilitate the onset of DNA replication (Keiler and Shapiro 2003a,b;Holtzendorff et al 2004;Collier et al 2006).…”

Cell pole–specific activation of a critical bacterial cell cycle kinase

“…β-galactosidase assays were conducted as described previously (25). LacZ synthesis was measured by performing [ 35 S]-methionine pulse experiments as described previously (26). Before G1-phase cell synchrony [performed as described previously (27)], the culture was incubated with 0.3% xylose overnight, and xylose was present during the [ 35 S]-methionine pulse experiment.…”

The Caulobacter crescentus ctrA P1 promoter is essential for the coordination of cell cycle events that prevent the overinitiation of DNA replication

“…Once a swarmer cell is exposed to sufficient nutrients, it differentiates into a stalked cell. As part of this transition, CtrA is degraded by the dynamically localizing protease ClpXP Jenal & Fuchs, 1998;McGrath et al, 2006), while DnaA continues to accumulate (Collier et al, 2006(Collier et al, , 2007. Without CtrA to block DnaA binding to the origin of replication, activated DnaA (Collier & Shapiro, 2009;Jonas et al, 2011) initiates DNA replication and activates the transcription of genes at the swarmer-to-stalked cell transition (Hottes et al, 2005).…”

“…Without CtrA to block DnaA binding to the origin of replication, activated DnaA (Collier & Shapiro, 2009;Jonas et al, 2011) initiates DNA replication and activates the transcription of genes at the swarmer-to-stalked cell transition (Hottes et al, 2005). One of these genes encodes GcrA, which activates or represses different genetic modules in stalked cells (Collier et al, 2006;Hottes et al, 2005). GcrA in turn inhibits the production of DnaA (Holtzendorff et al, 2004).…”