In vivo phosphorylation patterns of key stressosome proteins define a second feedback loop that limits activation of Bacillus subtilis					σB

Eymann, Christine; Schulz, Stephan; Gronau, Katrin; Becher, Dörte; Hecker, Michael; Price, Chester W.

doi:10.1111/j.1365-2958.2011.07609.x

Cited by 37 publications

(66 citation statements)

References 31 publications

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“…Alteration of the conserved serine in RsbS (S59A) significantly weakens activation of the response, suggesting that S59 phosphorylation is important but not essential for signaling in otherwise wild-type cells (23). Similar alterations to conserved threonines in RsbRA, the prototype of the RsbR family, support the inference that phosphorylation of T171 is a prerequisite for signaling but does not by itself trigger the response; in contrast, the additional phosphorylation of T205 appears to attenuate the response in the face of extreme environmental stress (16,24).…”

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confidence: 63%

“…The stressosome is thought to regulate the kinase activity of RsbT during the response, and RsbT phosphorylates the STAS domains of the RsbS and RsbR proteins on conserved serine and threonine residues, contributing to RsbT release (10,16,18,35). Alteration of the conserved serine in RsbS (S59A) significantly weakens activation of the response, suggesting that S59 phosphorylation is important but not essential for signaling in otherwise wild-type cells (23).…”

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confidence: 99%

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Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

Gaidenko

Bie

Baldwin

et al. 2011

Journal of Bacteriology

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The stressosome is a multiprotein, 1.8-MDa icosahedral complex that transmits diverse environmental signals to activate the general stress response of Bacillus subtilis. The way in which it senses these cues and the pathway of signal propagation within the stressosome itself are poorly understood. The stressosome core consists of four members of the RsbR coantagonist family together with the RsbS antagonist; its cryo-electron microscopy (cryoEM) image suggests that the N-terminal domains of the RsbR proteins form homodimers positioned to act as sensors on the stressosome surface. Here we probe the role of the N-terminal domain of the prototype coantagonist RsbRA by making structure-based amino acid substitutions in potential interaction surfaces. To unmask the phenotypes caused by single-copy rsbRA mutations, we constructed strains lacking the other three members of the RsbR coantagonist family and assayed system output using a reporter fusion. Effects of five individual alanine substitutions in the prominent dimer groove did not match predictions from an earlier in vitro assay, indicating that the in vivo assay was necessary to assess their influence on signaling. Additional substitutions expected to negatively affect domain dimerization had substantial impact, whereas those that sampled other prominent surface features had no consequence. Notably, even mutations resulting in significantly altered phenotypes raised the basal level of system output only in unstressed cells and had little effect on the magnitude of subsequent stress signaling. Our results provide evidence that the N-terminal domain of the RsbRA coantagonist affects stressosome function but offer no direct support for the hypothesis that it is a signal sensor.

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confidence: 63%

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Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

Gaidenko

Bie

Baldwin

et al. 2011

Journal of Bacteriology

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“…Partner switching upon phosphorylation and dephosphorylation is the main regulatory mechanism of this protein cluster in response to stresses. This has been studied mostly in B. subtilis (12)(13)(14) and seldom in L. monocytogenes. In unstressed B. subtilis, RsbW sequesters B into an association that prevents it from interacting with RNA polymerase.…”

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confidence: 99%

To Modulate Survival under Secondary Stress Conditions, Listeria monocytogenes 10403S Employs RsbX To Downregulate σ ^B Activity in the Poststress Recovery Stage or Stationary Phase

Xia

Xin

et al. 2016

Appl Environ Microbiol

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Listeria monocytogenes is a saprophytic bacterium that thrives in diverse environments and causes listeriosis via ingestion of contaminated food. RsbX, a putative sigma B ( B ) regulator, is thought to maintain the ready state in the absence of stress and reset the bacterium to the initial state in the poststress stage in Bacillus subtilis. We wondered whether RsbX is functional in L. monocytogenes under different stress scenarios. Genetic deletion and complementation of the rsbX gene were combined with survival tests and transcriptional and translational analyses of B expression in response to stresses. We found that deletion of rsbX increased survival under secondary stress following recovery of growth after primary stress or following stationary-phase culturing. The ⌬rsbX mutant had higher expression of B than its parent strain in the recovery stage following primary sodium stress and in stationary-phase cultures. Apparently, increased B expression had contributed to improved survival in the absence of RsbX. There were no significant differences in survival rates or B expression levels in response to primary stresses between the rsbX mutant and its parent strain during the exponential phase. Therefore, we provide clear evidence that RsbX is a negative regulator of L. monocytogenes B during the recovery period after a primary stress or in the stationary phase, thus affecting its survival under secondary stress. Listeria monocytogenes causes listeriosis in humans, mostly due to consumption of contaminated foods. As a saprophytic bacterium thriving in diverse environments, L. monocytogenes can survive and grow over a wide range of environmental conditions, including temperatures from Ϫ0.4 to 45°C, pH as low as 2.5, and high osmolarity (10% to 20% NaCl) (1-4). The general stressresponsive alternative sigma factor sigma B ( B ), which was first identified in Bacillus subtilis (5), plays a pivotal role in its resistance to environmental stresses (6, 7).B is coexpressed with seven of its principal regulators (regulators of sigma B rsbR, rsbS, rsbT, rsbU, rsbV, rsbW, and rsbX) in B. subtilis (8) and L. monocytogenes (9-11). Partner switching upon phosphorylation and dephosphorylation is the main regulatory mechanism of this protein cluster in response to stresses. This has been studied mostly in B. subtilis (12)(13)(14) and seldom in L. monocytogenes. In unstressed B. subtilis, RsbW sequesters B into an association that prevents it from interacting with RNA polymerase. RsbV is dephosphorylated by RsbU or RsbP in response to environmental or metabolic stress, respectively (15, 16). The dephosphorylated RsbV is capable of competing for RsbW, resulting in B liberation. The upstream proteins RsbT, RsbS, and RsbR form a complex called the "stressosome" in B. subtilis (17)(18)(19). Environmental stresses stimulate the kinase activity of RsbT, which can then be released from the stressosome available to activate RsbU (20).However, the interactions of these regulatory proteins in L. monocytogenes under stresses are not well...

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“…The key interactions that control σ B activation have been elucidated (24)(25)(26)(27). σ B is directly regulated by RsbW, an anti-sigma factor.…”

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Rate of environmental change determines stress response specificity

Young

Locke

Elowitz

2013

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

116

142

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Cells use general stress response pathways to activate diverse target genes in response to a variety of stresses. However, general stress responses coexist with more specific pathways that are activated by individual stresses, provoking the fundamental question of whether and how cells control the generality or specificity of their response to a particular stress. Here we address this issue using quantitative time-lapse microscopy of the Bacillus subtilis environmental stress response, mediated by σ B . We analyzed σ B activation in response to stresses such as salt and ethanol imposed at varying rates of increase. Dynamically, σ B responded to these stresses with a single adaptive activity pulse, whose amplitude depended on the rate at which the stress increased. This rate-responsive behavior can be understood from mathematical modeling of a key negative feedback loop in the underlying regulatory circuit. Using RNAseq we analyzed the effects of both rapid and gradual increases of ethanol and salt stress across the genome. Because of the rate responsiveness of σ B activation, salt and ethanol regulons overlap under rapid, but not gradual, increases in stress. Thus, the cell responds specifically to individual stresses that appear gradually, while using σ B to broaden the cellular response under more rapidly deteriorating conditions. Such dynamic control of specificity could be a critical function of other general stress response pathways.systems biology | single-cell dynamics | computational biology C ells must respond to, and anticipate, a wide range of stresses that occur on multiple timescales. For this purpose, many species use general stress response pathways, which activate a diverse set of target regulons in response to a variety of stresses. For example, in mammals, p53 is activated by DNA damage (1-4) and hypoxia (5, 6), among others, and activates genes that impact cell cycle progression (7), DNA repair (8, 9), apoptosis, and angiogenesis (10, 11). In yeast, Msn2/4 responds to nutritional stress (12), as well as to salt (13), calcium (14), heat, and other stresses (15). Bacteria also contain general stress response pathways, including the alternative sigma factors RpoS in Escherichia coli (16) and σ B in Bacillus subtilis (17).It has been proposed that general stress response pathways enable cells to cross-protect, by anticipating stresses that may not be present at the moment, but are likely to occur soon (18). For example, preexposure to specific stresses is known to enhance bacterial resistance to different stresses applied subsequently (19)(20)(21). This raises a basic question: How do cells determine when to use the general stress response rather than activating more specific individual pathways?The σ B -mediated general stress response of B. subtilis provides an ideal model system to address these issues. σ B is activated by diverse stresses through a well-characterized and conserved transcriptional and posttranscriptional circuit mechanism (17). In response to stress, it activates ∼200 target ge...

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In vivo phosphorylation patterns of key stressosome proteins define a second feedback loop that limits activation of Bacillus subtilis σ^B

Cited by 37 publications

References 31 publications

Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

To Modulate Survival under Secondary Stress Conditions, Listeria monocytogenes 10403S Employs RsbX To Downregulate σ ^B Activity in the Poststress Recovery Stage or Stationary Phase

Rate of environmental change determines stress response specificity

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In vivo phosphorylation patterns of key stressosome proteins define a second feedback loop that limits activation of Bacillus subtilis σB

Cited by 37 publications

References 31 publications

Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

Substitutions in the Presumed Sensing Domain of the Bacillus subtilis Stressosome Affect Its Basal Output but Not Response to Environmental Signals

To Modulate Survival under Secondary Stress Conditions, Listeria monocytogenes 10403S Employs RsbX To Downregulate σ B Activity in the Poststress Recovery Stage or Stationary Phase

Rate of environmental change determines stress response specificity

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In vivo phosphorylation patterns of key stressosome proteins define a second feedback loop that limits activation of Bacillus subtilis σ^B

To Modulate Survival under Secondary Stress Conditions, Listeria monocytogenes 10403S Employs RsbX To Downregulate σ ^B Activity in the Poststress Recovery Stage or Stationary Phase