Interaction of a redox-sensitive DNA-binding factor with the 5'-flanking region of the micF gene in Escherichia coli.

The product of the micF gene is an endogenous antisense RNA which down-regulates the expression of a major outer membrane protein, OmpF, in E. coli. We report here that two DNA-binding factors compete for the same site in the promoter region of the micF gene: RSBF, a high-affinity redox-sensitive DNA-binding factor that responds to an active oxygen species other than hydrogen peroxide or superoxide anions; and HRBF a heat-resistant DNA-binding factor. Both RSBF and HRBF bind to the same DNA sequence, 5'-TTAAAATCAATAACTTATTCTTAA3-', located upstream of the transcription start site of the micF gene. We present evidence that RSBF could be the controlling factor of a novel regulon involved in the response to oxidative stress in E. coli.