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Dive into the research topics where Regine Hengge-Aronis is active.

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Featured researches published by Regine Hengge-Aronis.


Microbiology and Molecular Biology Reviews | 2002

Signal transduction and regulatory mechanisms involved in control of the sigma(S) (RpoS) subunit of RNA polymerase.

Regine Hengge-Aronis

SUMMARY The σS (RpoS) subunit of RNA polymerase is the master regulator of the general stress response in Escherichia coli and related bacteria. While rapidly growing cells contain very little σS, exposure to many different stress conditions results in rapid and strong σS induction. Consequently, transcription of numerous σS-dependent genes is activated, many of which encode gene products with stress-protective functions. Multiple signal integration in the control of the cellular σS level is achieved by rpoS transcriptional and translational control as well as by regulated σS proteolysis, with various stress conditions differentially affecting these levels of σS control. Thus, a reduced growth rate results in increased rpoS transcription whereas high osmolarity, low temperature, acidic pH, and some late-log-phase signals stimulate the translation of already present rpoS mRNA. In addition, carbon starvation, high osmolarity, acidic pH, and high temperature result in stabilization of σS, which, under nonstress conditions, is degraded with a half-life of one to several minutes. Important cis-regulatory determinants as well as trans-acting regulatory factors involved at all levels of σS regulation have been identified. rpoS translation is controlled by several proteins (Hfq and HU) and small regulatory RNAs that probably affect the secondary structure of rpoS mRNA. For σS proteolysis, the response regulator RssB is essential. RssB is a specific direct σS recognition factor, whose affinity for σS is modulated by phosphorylation of its receiver domain. RssB delivers σS to the ClpXP protease, where σS is unfolded and completely degraded. This review summarizes our current knowledge about the molecular functions and interactions of these components and tries to establish a framework for further research on the mode of multiple signal input into this complex regulatory system.


Current Opinion in Microbiology | 1999

Interplay of global regulators and cell physiology in the general stress response of Escherichia coli

Regine Hengge-Aronis

Under various stress conditions, two sigma subunits of RNA polymerase, sigmaS and sigma70, coexist in Escherichia coli cells. In contrast to sigma70, sigmaS is subject to intricate regulation and coordinates an emergency reaction to stress as well as long term stress adaptation. In vivo, the two sigma factors clearly control different genes. Yet, they are structurally and functionally very similar and basically recognize the same promoter sequences. Recent data suggest that sigma factor specificity at stress-activated promoters is affected by the interplay of the two RNA polymeraseholoenzymes with additional regulatory factors, such as H-NS, Lrp, CRP, IHF or Fis, that differentially affect transcription initiation by sigmaS or sigma70 in a promoter-specific manner.


Current Opinion in Microbiology | 2003

Regulation by proteolysis in bacterial cells

Urs Jenal; Regine Hengge-Aronis

Regulation by proteolysis plays a major role in bacterial stress responses, the cell cycle and development. Key regulators of these processes are subject to conditional proteolysis that depends on complex cellular information processing. This information includes temporal and spatial cues, and recent research has revealed a striking potential for multiple signal integration.


Current Opinion in Microbiology | 2002

Stationary phase gene regulation: what makes an Escherichia coli promoter σS-selective?

Regine Hengge-Aronis

The general stress sigma factor sigma(S) and the vegetative sigma(70) are highly related and recognise the same core promoter elements. Nevertheless, they clearly control different sets of genes in vivo. Recent studies have demonstrated that Esigma(S) selectivity is based on modular combinations of several sequence and structural features of a promoter, to which also trans-acting factors can strongly contribute. These results throw novel light on the details of transcription initiation, as well as on the co-evolution of sigma factors and their cognate promoter sequences.


Molecular Microbiology | 2001

What makes an Escherichia coli promoter σS dependent? Role of the −13/−14 nucleotide promoter positions and region 2.5 of σS

Gisela Becker; Regine Hengge-Aronis

The σS and σ70 subunits of Escherichia coli RNA polymerase recognize very similar promoter sequences. Therefore, many promoters can be activated by both holoenzymes in vitro. The same promoters, however, often exhibit distinct sigma factor selectivity in vivo. It has been shown that high salt conditions, reduced negative supercoiling and the formation of complex nucleoprotein structures in a promoter region can contribute to or even generate σS selectivity. Here, we characterize the first positively acting σS‐selective feature in the promoter sequence itself. Using the σS‐dependent csiD promoter as a model system, we demonstrate that C and T at the −13 and −14 positions, respectively, result in strongest expression. We provide allele‐specific suppression data indicating that these nucleotides are contacted by K173 in region 2.5 of σS. In contrast, σ70, which features a glutamate at the corresponding position (E458), as well as the σS(K173E) variant, exhibit a preference for a G(−13). C(−13) is highly conserved in σS‐dependent promoters, and additional data with the osmY promoter demonstrate that the K173/C(−13) interaction is of general importance. In conclusion, our data demonstrate an important role for region 2.5 in σS in transcription initiation. Moreover, we propose a consensus sequence for a σS‐selective promoter and discuss its emergence and functional properties from an evolutionary point of view.


Molecular Microbiology | 2001

The Escherichia coli histone‐like protein HU regulates rpoS translation

Anna Balandina; Laurent Claret; Regine Hengge-Aronis; Josette Rouviere-Yaniv

Escherichia coli HU protein is a major component of the bacterial nucleoid. HU stabilizes higher order nucleoprotein complexes and belongs to a family of DNA architectural proteins. Here, we report that HU is required for efficient expression of the sigma S subunit of RNA polymerase. This rpoS‐encoded alternative σS factor induces a number of genes implicated in cell survival in stationary phase and in multiple stress resistance. By analysis of rpoS–lacZ fusions and by pulse‐chase experiments, we show that the efficiency of rpoS translation is reduced in cells lacking HU, whereas neither rpoS transcription nor protein stability is affected by HU. Gel mobility shift assays show that HU is able to bind specifically an RNA fragment containing the translational initiation region of rpoS mRNA 1000‐fold more strongly than double‐stranded DNA. Together with the in vivo data, this finding strongly suggests that, by binding to rpoS mRNA, HU directly stimulates rpoS translation. We demonstrate here that HU, an abundant DNA‐binding, histone‐like protein, is able specifically to recognize an RNA molecule and therefore play a role in post‐transcriptional regulation.


The EMBO Journal | 2000

σ factor selectivity of Escherichia coli RNA polymerase: role for CRP, IHF and Lrp transcription factors

Frédéric Colland; Mechthild Barth; Regine Hengge-Aronis; Annie Kolb

osmY is a stationary phase‐induced and osmotically regulated gene in Escherichia coli that requires the stationary phase RNA polymerase (EσS) for in vivo expression. We show here that the major RNA polymerase, Eσ70, also transcribes osmY in vitro and, depending on genetic background, even in vivo. The cAMP receptor protein (CRP) bound to cAMP, the leucine‐responsive regulatory protein (Lrp) and the integration host factor (IHF) inhibit transcription initiation at the osmY promoter. The binding site for CRP is centred at −12.5 from the transcription start site, whereas Lrp covers the whole promoter region. The site for IHF maps in the −90 region. By mobility shift assay, permanganate reactivity and in vitro transcription experiments, we show that repression is much stronger with Eσ70 than with EσS holoenzyme. We conclude that CRP, Lrp and IHF inhibit open complex formation more efficiently with Eσ70 than with EσS. This different ability of the two holoenzymes to interact productively with promoters once assembled in complex nucleoprotein structures may be a crucial factor in generating σS selectivity in vivo.


Molecular Microbiology | 2002

The response regulator RssB, a recognition factor for σS proteolysis in Escherichia coli, can act like an anti-σS factor

Gisela Becker; Eberhard Klauck; Regine Hengge-Aronis

σS (RpoS) is the master regulator of the general stress response in Escherichia coli. Several stresses increase cellular σS levels by inhibiting proteolysis of σS, which under non‐stress conditions is a highly unstable protein. For this ClpXP‐dependent degradation, the response regulator RssB acts as a recognition factor, with RssB affinity for σS being modulated by phosphorylation. Here, we demonstrate that RssB can also act like an anti‐sigma factor for σSin vivo, i.e. RssB can inhibit the expression of σS‐dependent genes in the presence of high σS levels. This becomes apparent when (i) the cellular RssB/σS ratio is at least somewhat elevated and (ii) proteolysis is reduced (for example in stationary phase) or eliminated (for example in a clpP mutant). Two modes of inhibition of σS by RssB can be distinguished. The ‘catalytic’ mode is observed in stationary phase cells with a substoichiometric RssB/σS ratio, requires ClpP and therefore probably corresponds to sequestering of σS to Clp protease (even though σS is not degraded). The ‘stoichiometric’ mode occurs in clpP mutant cells upon overproduction of RssB to levels that are equal to those of σS, and therefore probably involves binary complex formation between RssB and σS. We also show that, under standard laboratory conditions, the cellular level of RssB is more than 20‐fold lower than that of σS and is not significantly controlled by stresses that upregulate σS. We therefore propose that antisigma factor activity of RssB may play a role under not yet identified growth conditions (which may result in RssB induction), or that RssB is a former antisigma factor that during evolution was recruited to serve as a recognition factor for proteolysis.


Molecular Microbiology | 2001

Role of the response regulator RssB in σS recognition and initiation of σS proteolysis in Escherichia coli

Eberhard Klauck; Maren Lingnau; Regine Hengge-Aronis

In growing Escherichia coli cells, the master regulator of the general stress response, σS (RpoS), is subject to rapid proteolysis. In response to stresses such as sudden carbon starvation, osmotic upshift or shift to acidic pH, σS degradation is inhibited, σS accumulates and numerous σS‐dependent genes with stress‐protective functions are activated. σS proteolysis is dependent on ClpXP protease and the response regulator RssB, whose phosphorylated form binds directly to σSin vitro. Here, we show that substitutions of aspartate 58 (D58) in RssB, which result in higher σS levels in vivo, produce RssB variants unable to bind σSin vitro. Thus, RssB is the direct substrate recognition factor in σS proteolysis, whose affinity for σS depends on phosphorylation of its D58 residue. RssB does not dimerize or oligomerize upon this phosphorylation and σS binding, and RssB and σS exhibit a 1:1 stoichiometry in the complex. The receiver as well as the output domain of RssB are required for σS binding (as shown in vivo and in vitro) and for complementation of an rssB null mutation. Thus, the N‐terminal receiver domain plays an active and positive role in RssB function. Finally, we demonstrate that RssB is not co‐degraded with σS, i.e. RssB has a catalytic role in the initiation of σS turnover. A model is presented that integrates the details of RssB–σS interaction, the RssB catalytic cycle and potential stress signal input in the control of σS proteolysis.


Molecular Microbiology | 2002

The cellular level of the recognition factor RssB is rate‐limiting for σS proteolysis: implications for RssB regulation and signal transduction in σS turnover in Escherichia coli

Mihaela Pruteanu; Regine Hengge-Aronis

Degradation of the general stress sigma factor σS of Escherichia coli is a prime example of regulated proteolysis in prokaryotes. Whereas exponentially growing cells rapidly degrade σS, various stress conditions result in stabilization and, therefore, rapid accumulation of σS. Proteolysis of σS requires the response regulator RssB, a direct recognition factor with phosphorylation‐dependent affinity for σS, which targets σS to the ClpXP protease. Here, we demonstrate that a sudden increase in σS synthesis results in σS stabilization, indicating titration of an essential proteolytic component. Evidence is provided that RssB is the overall rate‐limiting factor for σS proteolysis. As a consequence, the cell has to continuously adjust the expression of RssB to σS in order to maintain σS proteolysis in growing cells, despite variations in the rate of σS synthesis. Such homeostatic feedback‐coupling is provided by rssB transcription being dependent on the σS‐controlled rssAB operon promoter. However, strong and rapid increases in σS synthesis, in re‐sponse to acute stress, exceed the compensatory potential of this feedback loop with the result that σS is stabilized because of RssB titration. We propose that RssB control of σS proteolysis functions as a genetic switch, in which (i) the ‘off’ state (low σS levels caused by proteolysis) is stabilized by a homeostatic negative feedback, and (ii) the threshold for switching to the ‘on’ state (high levels of stable σS) is dependent on the cellular level of active, i.e. phosphorylated RssB.

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Gisela Becker

Free University of Berlin

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Eberhard Klauck

Free University of Berlin

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Jens Germer

Free University of Berlin

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Maren Lingnau

Free University of Berlin

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Martin Metzner

Free University of Berlin

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Anna Balandina

Centre national de la recherche scientifique

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