Continuous Control in Bacterial Regulatory Circuits

Batchelor, Eric; Silhavy, Thomas J.; Goulian, Mark

doi:10.1128/jb.186.22.7618-7625.2004

Cited by 42 publications

(55 citation statements)

References 46 publications

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“…To monitor transcription of the porin genes ompF and ompC, we used the two-color fluorescent reporter strain MDG147, which contains chromosomal operon fusions of yfp to ompF and cfp to ompC (5). We observed that colonies of MDG147 growing on medium A agar plates initially showed uniform CFP and YFP fluorescence.…”

Section: Resultsmentioning

confidence: 99%

The Escherichia coli CpxA-CpxR Envelope Stress Response System Regulates Expression of the Porins OmpF and OmpC

Batchelor¹,

et al. 2005

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We performed transposon mutagenesis of a two-color fluorescent reporter strain to identify new regulators of the porin genes ompF and ompC in Escherichia coli. Screening of colonies by fluorescence microscopy revealed numerous mutants that exhibited interesting patterns of porin expression. One mutant harbored an insertion in the gene encoding the histidine kinase CpxA, the sensor for a two-component signaling system that responds to envelope stress. The cpxA mutant exhibited increased transcription of ompC and a very strong decrease in transcription of ompF under conditions in which acetyl phosphate levels were high. Subsequent genetic analysis revealed that this phenotype is dependent on phosphorylation of the response regulator CpxR and that activation of CpxA in wild-type cells results in similar regulation of porin expression. Using DNase I footprinting, we demonstrated that CpxR binds upstream of both the ompF and ompC promoters. It thus appears that two distinct two-component systems, CpxA-CpxR and EnvZ-OmpR, converge at the porin promoters. Within the context of envelope stress, outer membrane beta-barrel proteins have generally been associated with the sigma E pathway. However, at least for the classical porins OmpF and OmpC, our results show that the Cpx envelope stress response system plays a role in regulating their expression.The classical porins OmpF and OmpC are major constituents of the Escherichia coli outer membrane and account for approximately 2% of the total protein content of the cell (52). These proteins allow for the passive diffusion of solutes across the outer membrane. Many environmental factors have been identified that alter OmpF and OmpC expression, including osmolarity, temperature, pH, nutrient availability, and various toxins (23,40,54). The importance of this complex regulation for the cell is not understood, although it has been suggested that the differential regulation of the two porins may provide a means of balancing the competing needs of access to nutrients and protection from toxins (52).The complex environmental regulation of the porins is implemented by a similarly complex regulatory network, whose components include the EnvZ-OmpR two-component system (reviewed in references 19, 34, and 63), the small RNAs MicF and MicC (9, 14), the sigma factors S and E (45, 55), the global regulator Lrp (21), and the histone-like protein IHF (30, 59). The EnvZ-OmpR system is a central element of this network, since phosphorylated OmpR (OmpR-P) is absolutely required for OmpF and OmpC expression. OmpR-P levels are modulated by the histidine kinase EnvZ in response to unknown stimuli. Low levels of OmpR-P activate transcription of ompF, while high levels repress ompF and activate ompC (22,36,61). In vitro studies revealed that OmpR binds to three sites (designated C1, C2, and C3) upstream of the ompC promoter (41, 66) and four sites (one distal site, F4, and three proximal sites, F1, F2, and F3) upstream of the ompF promoter (28,29,48,66). However, despite this detailed characterizatio...

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Section: Resultsmentioning

confidence: 99%

The Escherichia coli CpxA-CpxR Envelope Stress Response System Regulates Expression of the Porins OmpF and OmpC

Batchelor¹,

et al. 2005

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“…Despite these findings, the effects of negative feedback (NF) on gene expression are not fully understood. For example, it was suggested that NF alters the shape of the dose-response curve in transcriptional cascades (22,25,26), but this effect has never been explored in detail. Such knowledge is vital for the rational design and characterization of increasingly complex transcriptional networks via bottom-up approaches in synthetic biology (27)(28)(29)(30).…”

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Negative autoregulation linearizes the dose–response and suppresses the heterogeneity of gene expression

Nevozhay

Adams

Murphy

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

318

394

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“…New investigative approaches and mathematical analyses are revealing that regulatory complexity has important functional consequences, which include asymmetric kinetics (26), robust control (27), graded responses (28), and the generation of noise (29). As Emerson observed (30), ''The highest simplicity of structure is produced, not by few elements, but by the highest level of complexity.''…”

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confidence: 99%

Sigma cascades in prokaryotic regulatory networks

Fang

2005

Proc. Natl. Acad. Sci. U.S.A.

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Continuous Control in Bacterial Regulatory Circuits

Cited by 42 publications

References 46 publications

The Escherichia coli CpxA-CpxR Envelope Stress Response System Regulates Expression of the Porins OmpF and OmpC

The Escherichia coli CpxA-CpxR Envelope Stress Response System Regulates Expression of the Porins OmpF and OmpC

Negative autoregulation linearizes the dose–response and suppresses the heterogeneity of gene expression

Sigma cascades in prokaryotic regulatory networks

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