Screening of promoter-specific transcription factors: multiple regulators for the sdiA gene involved in cell division control and quorum sensing.

Prokaryotic DNA-binding transcription factors (TFs) bind in close vicinity of the promoter and regulate transcription through interplay with the DNA-dependent RNA polymerase. Promoters associated with the genes involved in stress response have recently been found to be under the control of multiple regulators, each monitoring one specific environmental condition or factor. In order to identify TFs involved in regulation of one specific promoter, we have developed a PS-TF (promoter-specific TF) screening system, in which the binding of purified TFs to a test promoter was analysed by gel-shift assay. This PS-TF screening system was applied for detection of TFs involved in regulation of the promoter for the Escherichia coli sdiA gene encoding the master regulator of cell division and quorum sensing. After screening of a total of 191 purified TFs (two-thirds of the predicted E. coli TFs), at least 15 TFs have been identified to bind to the sdiA promoter, including five two-component system (TCS) regulators, ArcA, CpxR, OmpR, RcsB and TorR. In this study, we focus on these five TFs for detailed analysis of their regulatory roles in vivo. Under normal growth conditions in LB medium, all these TFs repressed the sdiA promoter and the repression levels correlated with their intracellular levels. Taken together, we propose that these TCS regulators repress transcription in vivo of the sdiA gene, ultimately leading to suppression of cell division.