| Autor: |
Bordes, Patricia, Conter, Annie, Morales, Violette, Bouvier, Jean, Kolb, Annie, Gutierrez, Claude |
| Předmět: |
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| Zdroj: |
Molecular Microbiology; Apr2003, Vol. 48 Issue 2, p561, 11p |
| Abstrakt: |
Summary: The σ[sup S] subunit of RNA polymerase is a key regulator of Escherichia coli transcription in stress conditions. σ[sup 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[sup S] accumulates long before the beginning of the σ[sup S]-dependent induction of osmE[sub 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[sup S]. The variations in superhelical densities occurring as a function of growth conditions can modulate transcription of a subset of σ[sup S] targets and thereby contribute to the temporal disconnection between the accumulation of σ[sup S] and σ[sup S]-driven transcription. We propose that, in stress conditions leading to the accumulation of σ[sup S] without lowering the growth rate, the level of DNA supercoiling acts as a checkpoint that delays the shift from the major (Eσ[sup 70]) to the general stress (Eσ[sup S]) transcriptional machinery, retarding the induction of a subset of the σ[sup S] regulon until the conditions become unfavourable enough to cause entry into stationary phase.. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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