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Involvement of differential efficiency of transcription by Eσ s and Eσ 70 RNA polymerase holoenzymes in growth phase regulation of the Escherichia coli osmE promoter
Author(s) -
Bordes Patricia,
Repoila Francis,
Kolb Annie,
Gutierrez Claude
Publication year - 2000
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2000.01758.x
Subject(s) - biology , promoter , rpos , sigma factor , rna polymerase , transcription (linguistics) , gene , escherichia coli , regulon , genetics , microbiology and biotechnology , gene expression , linguistics , philosophy
Transcription of the gene osmE of Escherichia coli is inducible by elevated osmotic pressure and during the decelerating phase of growth. osmE expression is directed by a single promoter, osmE p . Decelerating phase induction of osmE p is dependent on the σ s (RpoS) factor, whereas its osmotic induction is independent of σ s. Purified Eσ s and Eσ 70 were both able to transcribe osmE p in vitro on supercoiled templates. In the presence of rpoD800 , a mutation resulting in a thermosensitive σ 70 factor, a shift to non‐permissive temperature abolished induction of osmE p after an osmotic shock during exponential phase, but did not affect the decelerating phase induction. Point mutations affecting osmE p activity were isolated. Down‐promoter mutations decreased transcription in both the presence and the absence of σ s , indicating that the two forms of RNA polymerase holoenzyme recognize very similar sequence determinants on the osmE promoter. Three up‐promoter mutations brought osmE p closer to the consensus of Eσ 70 ‐dependent promoters. The two variant promoters exhibiting the highest efficiency became essentially independent of σ s in vivo . Our data suggest that Eσ s transcribes wild‐type osmE p with a higher efficiency than Eσ 70. A model in which an intrinsic differential recognition contributes to growth phase‐dependent regulation is proposed. Generalization of this model to other σ s ‐dependent promoters is discussed.