A differential effect of sigma super(S) on the expression of the PHO regulon genes of Escherichia coli

• Published in: Microbiology (Society for General Microbiology) 2004-09, Vol.150 (9), p.2985-2992
• Main Authors: Taschner, N P, Yagil, E, Spira, B
• Format: Article
• Language: English
• Subjects: Escherichia coli
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.27124-0

The RNA polymerase core associated with sigma super(S) transcribes many genes related to stress or to the stationary phase. When cells enter a phase of phosphate starvation, the transcription of several genes and operons, collectively known as the PHO regulon, is strongly induced. The promoters of the PHO genes hitherto analysed are recognized by sigma super(D)-associated RNA polymerase. A mutation in the gene that encodes sigma super(S), rpoS, significantly increases the level of alkaline phosphatase activity and the overproduction of sigma super(S) inhibits it. Other PHO genes such as phoE and ugpB are likewise affected by sigma super(S). In contrast, pstS, which encodes a periplasmic phosphate-binding protein and is a negative regulator of PHO, is stimulated by sigma super(S). The effect of sigma super(S) on the PHO genes is at the transcriptional level. It is shown that a cytosine residue at position -13 is important for the positive effect of sigma super(S) on pst. The interpretation of these observations is based on the competition between sigma super(S) and sigma super(D) for the binding to the core RNA polymerase.