Conserved regulatory elements of the promoter sequence of the gene rpoH of enteric bacteria

The rpoH regulatory region of different members of the enteric bacteria family was sequenced or downloaded from GenBank and compared. In addition, the transcriptional start sites of rpoH of Yersinia frederiksenii and Proteus mirabilis, two distant members of this family, were determined. Sequences similar to the σ(70) promoters P1, P4 and P5, to the σ(E) promoter P3 and to boxes DnaA1, DnaA2, cAMP receptor protein (CRP) boxes CRP1, CRP2 and box CytR present in Escherichia coli K12, were identified in sequences of closely related bacteria such as: E.coli, Shigella flexneri, Salmonella enterica serovar Typhimurium, Citrobacter freundii, Enterobacter cloacae and Klebsiella pneumoniae. In more distant bacteria, Y.frederiksenii and P.mirabilis, the rpoH regulatory region has a distal P1-like σ(70) promoter and two proximal promoters: a heat-induced σ(E)-like promoter and a σ(70) promoter. Sequences similar to the regulatory boxes were not identified in these bacteria. This study suggests that the general pattern of transcription of the rpoH gene in enteric bacteria includes a distal σ(70) promoter, >200 nt upstream of the initiation codon, and two proximal promoters: a heat-induced σ(E)-like promoter and a σ(70) promoter. A second proximal σ(70) promoter under catabolite-regulation is probably present only in bacteria closely related to E.coli.