, Volume 185, Issue 3, pp 234-237
Date: 11 Jan 2006

The effect of IHF on σ S selectivity of the phoA and pst promoters of Escherichia coli

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The pst operon, a member of the PHO regulon of Escherichia coli, encodes a high-affinity phosphate transport system whose expression is induced when the cells enter a phase of phosphate starvation. The expression of pst is stimulated by the integration host factor (IHF). Transcription of the PHO regulon genes is initiated by the RNA polymerase complexed with σ D (Eσ D). Owing to a cytosine residue at position −13 of the pst promoter its transcription can also be initiated by Eσ S. Here, we show that inactivation of IHF in vivo abolishes the σ S-dependent transcription initiation of the pst operon, indicating that both −13C residue and IHF are required to confer on pst the ability to be transcribed by Eσ S. Introduction of a −13C residue in the promoter region of phoA, another PHO regulon gene that is not directly affected by IHF, did not affect its exclusive transcription initiation by Eσ D.