• Transcriptional start site;
  • 70;
  • E


We previously determined the complete DNA sequence of the rpoH gene encoding the heat-shock σ factor (σH) of Pseudomonas putida. In the present study, the transcriptional start sites of rpoH were determined to be 41 nucleotides (T1), 153 nucleotides (T2) and 157 nucleotides (T3) upstream from the translational start codon (AUG) of rpoH by rapid amplification of cDNA 5′-ends. Based on the locations of T2 and T3, a σ70-type promoter (P2) was determined to be located in the open reading frame region of upstream ftsX in addition to the σE-type promoter (P1; DNA Res. 6 (1999) 241). In the in vitro transcription assay with reconstituted RNA polymerases (Eσ70, EσE, EσH and EσS) of Pseudomonas aeruginosa, EσE transcribed rpoH from T1 and Eσ70 transcribed it from T2 and T3. In both cases, the level of transcription was higher at 42°C than at 30°C. No transcript was detected when EσH or EσS was used. These results indicate that EσE and Eσ70 recognize P1 promoter and P2 promoter, respectively, and also prove that the synthesis of rpoH mRNA is inducible upon heat shock.