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DNA supercoiling contributes to disconnect σ S accumulation from σ S ‐dependent transcription in Escherichia coli
Author(s) -
Bordes Patricia,
Conter Annie,
Morales Violette,
Bouvier Jean,
Kolb Annie,
Gutierrez Claude
Publication year - 2003
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.1365-2958.2003.03461.x
Subject(s) - biology , regulon , transcription (linguistics) , rna polymerase , dna supercoil , microbiology and biotechnology , transcriptional regulation , osmotic shock , rpos , regulation of gene expression , dna , escherichia coli , gene , transcription factor , gene expression , promoter , genetics , dna replication , linguistics , philosophy
Summary The σ S subunit of RNA polymerase is a key regulator of Escherichia coli transcription in stress conditions. σ S accumulates in cells subjected to stresses such as an osmotic upshift or the entry into stationary phase. We show here that, at elevated osmolarity, σ S accumulates long before the beginning of the σ S ‐dependent induction of osmE p , one of its target promoters. A combination of in vivo and in vitro evidence indicates that a high level of DNA negative supercoiling inhibits transcription by Eσ S . The variations in superhelical densities occurring as a function of growth conditions can modulate transcription of a subset of σ S targets and thereby contribute to the temporal disconnection between the accumulation of σ S and σ S ‐driven transcription. We propose that, in stress conditions leading to the accumulation of σ S without lowering the growth rate, the level of DNA supercoiling acts as a checkpoint that delays the shift from the major (Eσ 70 ) to the general stress (Eσ S ) transcriptional machinery, retarding the induction of a subset of the σ S regulon until the conditions become unfavourable enough to cause entry into stationary phase.