A Genetic Oscillator and the Regulation of Cell Cycle Progression in Caulobacter crescentus

Analyses of cell polarity, division, and differentiation in prokaryotes have identified several regulatory proteins that exhibit dramatic changes in expression and spatial localization over the course of a cell cycle. The dynamic behavior of these proteins is often intrinsically linked to their function as polarity determinants. In the ?-proteobacterium, Caulobacter crescentus, the CtrA global transcriptional regulator exhibits a spatially and temporally dynamic expression pattern across the cell cycle. CtrA plays key roles in asymmetric cell division and in the timing of chromosome replication. An additional global regulator, GcrA, has recently been discovered that both regulates and is regulated by CtrA. Together, these regulatory proteins create a genetic circuit in which the cellular concentrations of CtrA and GcrA oscillate spatially and temporally to control daughter cell differentiation and cell cycle progression.