Temperature sensing by the dsrA promoter.

Synthesis of the small regulatory RNA DsrA is under temperature control. The minimal dsrA promoter of 36 bp contains sufficient information to ensure such regulation. In vivo, we have analyzed the critical elements responsible for the temperature control of dsrA by using a collection of chimeric promoters combining various elements of the dsrA promoter and the lacUV5 promoter, which does not respond to temperature. Our results favor an RNA polymerase-DNA interaction model instead of a trans-acting factor for temperature regulation. While all of the elements of the dsrA promoter contribute to temperature-sensitive expression, the sequence of the -10 box and the spacer region are the essential elements for the thermal response of the dsrA promoter. The proper context for these promoter elements, including at least one of the flanking elements, the -35 region or the start site region, is also required. Point mutations demonstrate that the sequence of the -10 box imposes constraints on the length and the sequence of the spacer and/or its AT richness, even at low temperature. These results show a complex interdependence of different regions in the promoter for temperature regulation.