 rpoSp promotes transcription of "rpoS" mRNA, and is induced upon entry into stationary phase in cells growing on rich media via an unknown mechanism.Flanking rpoSp are two putative cAMP-CRP (cyclic AMP-cAMP receptor protein) binding sites that seem to control "rpoS" transcription in an antagonistic manner.The position of the first site upstream of the major "rpoS" promoter corresponds to a “classical activator” similarly found in the "lac" promoter thereby suggesting that its effects on transcription are activating (Lange and Hengge-Aronis, 1994); in contrast, the location of the second cAMP-CRP site is indicative of inhibitory action.