FIG. 3.

Heat shock induction of RpoH is abolished by replacing the promoter. (A) Sequence of the rpoH promoter and part of the coding region (underlined) is shown. Lines *1 and *2 represent portions of the sequence that were used or deleted in constructing the transcriptional fusion PrpoH′-lacZ or Plac′-rpoH, respectively (see Materials and Methods). (B) Sequence of a synthetic promoter (Plac′) used to construct Plac′-rpoH, in which rpoH transcription is driven by Plac′. The Rho-independent terminator from E. coli trpA (underlined) (6) was fused to part of the E. coli lac promoter (nucleotides −35 to +1) to prevent readthrough from upstream. (C) A pair of strains with the chromosomal rpoH⁺ gene under the authentic rpoH promoter (KN207) or the Plac′ promoter (KN208) were grown in complete medium to log phase at 25°C and shifted to 37°C. Samples were taken before or after heat shock as indicated, treated, and analyzed by SDS-PAGE (10% polyacrylamide), and RpoH was detected by immunoblotting.