Signal Transduction Cascade for Regulation of RpoS: Temperature Regulation of DsrA

ABSTRACT Many environmental parameters modulate the amount of the RpoS sigma factor in Escherichia coli. Temperature control of RpoS depends on the untranslated RNA DsrA. DsrA activates RpoS translation by pairing with the leader of the mRNA. We find that temperature affects both the rate of transcription initiation of thedsrA gene and the stability of DsrA RNA. Both are increased at low temperature (25°C) compared to 37 or 42°C. The combination of these results is 25-fold-less DsrA at 37°C and 30-fold less at 42°C than at 25°C. Using an adaptedlacZ-based reporter system, we show that temperature control of transcription initiation of dsrA requires only the minimal promoter of 36 bp. Overall, transcription responses to temperature lead to a sixfold increase in DsrA synthesis at 25°C over that at 42°C. Furthermore, two activating regions and a site for LeuO negative regulation were identified in the dsrApromoter. The activating regions also activate transcription in vitro. DsrA decays with a half-life of 23 min at 25°C and 4 min at 37 and 42°C. These results demonstrate that the dsrA promoter and the stability of DsrA RNA are the thermometers for RpoS temperature sensing. Multiple inputs to DsrA accumulation allow sensitive modulation of changes in the synthesis of the downstream targets of DsrA such as RpoS.