Journal Article

Sigma E controls biogenesis of the antisense RNA MicA

Klas I. Udekwu and E. Gerhart H. Wagner

in Nucleic Acids Research

Volume 35, issue 4, pages 1279-1288
Published in print February 2007 | ISSN: 0305-1048
Published online January 2007 | e-ISSN: 1362-4962 | DOI: https://dx.doi.org/10.1093/nar/gkl1154
Sigma E controls biogenesis of the antisense RNA MicA

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  • Chemistry
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  • Molecular and Cell Biology

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Adaptation stress responses in the Gram-negative bacterium Escherichia coli and its relatives involve a growing list of small regulatory RNAs (sRNAs). Previous work by us and others showed that the antisense RNA MicA downregulates the synthesis of the outer membrane protein OmpA upon entry into stationary phase. This regulation is Hfq-dependent and occurs by MicA-dependent translational inhibition which facilitates mRNA decay. In this article, we investigate the transcriptional regulation of the micA gene. Induction of MicA is dependent on the alarmone ppGpp, suggestive of alternative σ factor involvement, yet MicA accumulates in the absence of the general stress/stationary phase σS. We identified stress conditions that induce high MicA levels even during exponential growth—a phase in which MicA levels are low (ethanol, hyperosmolarity and heat shock). Such treatments are sensed as envelope stress, upon which the extracytoplasmic sigma factor σE is activated. The strict dependence of micA transcription on σE is supported by three observations. Induced overexpression of σE increases micA transcription, an ΔrpoE mutant displays undetectable MicA levels and the micA promoter has the consensus σE signature. Thus, MicA is part of the σE regulon and downregulates its target gene, ompA, probably to alleviate membrane stress.

Journal Article.  6498 words.  Illustrated.

Subjects: Chemistry ; Biochemistry ; Bioinformatics and Computational Biology ; Genetics and Genomics ; Molecular and Cell Biology

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