The dps promoter is activated by OxyR during growth and by IHF and σs in stationary phase

Abstract

Dps is a non-specific DNA-binding protein abundant In starved Escherichia coli cells and is important for the defence against hydrogen peroxide. We found that dps mRNA levels are controlled by rpoS-encoded σ^s, the transcriptional activator OxyR and the histone-like IHF protein, in exponentially growing cells, dps is induced by treatment with hydrogen peroxide in an OxyR-dependent manner. This OxyR-dependent induction occurs only during log phase, although the OxyR protein is present in stationary phase, in the stationary phase cells, dps is expressed in a σ^s - and IHF-dependent manner. The purified OxyR and IHF proteins are also shown to bind upstream of the dps promoter. Our results suggest that the dps promoter is recognized by both σ⁷⁰-holoenzyme and σ^s-holoenzyme, since OxyR acts through σ⁷⁰ and the starts of the OxyR- and σ^s-dependent transcripts are identical.