Regulatory characteristics and promoter analysis of csiE, a stationary phase-inducible gene under the control of sigma S and the cAMP-CRP complex in Escherichia coli

Abstract

Sigma-S and the cAMP-CRP complex are global regulatory factors involved in stationary-phase induction of large groups of genes in Escherichia coli. csiE, a gene located at 57.25 min (co-ordinate 2674) of the physical map of the E. coli chromosome, is under the control of both of these factors. Sigma-S plays a positive, though not absolutely essential, role in the expression of csiE. Regulation by cAMP-CRP has both positive and negative elements, with the latter being dependent on the presence of sigma s, whose expression is negatively influenced by cAMP-CRP. csiE has a single transcriptional start site located 33 bp upstream of the initiation codon. By a 5'-deletion approach, we show that 72 bp upstream of the csiE transcriptional start site are sufficient for regulation by sigma s and cAMP-CRP. A deletion upstream of nucleotide -38 with respect to the start site eliminates positive cAMP-CRP control and makes the remaining expression fully dependent on sigma S. Our results indicate that transcription at the csiE promoter can be initiated in vivo by sigma S-containing RNA polymerase alone as well as by sigma 70-containing RNA polymerase in conjunction with cAMP-CRP or a cAMP-CRP-dependent secondary regulator. The promoter region of poxB, the structural gene for pyruvate oxidase, which is also under the control of sigma S and cAMP-CRP, is very similar to the corresponding region of csiE, suggesting a similar regulatory mechanism also for poxB.