QsIA disrupts LasR dimerization in antiactivation of bacterial quorum sensing

Fan, Haijun; Dong, Ying; Wu, Donghui; Bowler, Matthew W.; Zhang, Lian-Hui; Song, Haiwei

doi:10.1073/pnas.1314415110

Cited by 42 publications

(43 citation statements)

References 48 publications

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“…TraM binds the DNAbinding domain of TraR on the opposite side of the DNAbinding surface (46,47). More recently, structural characterization of the LasR-binding antiactivator QslA of Pseudomonas aeruginosa (48) revealed that in contrast to TraM, QslA binds the ligand-binding domain of LasR (48). Thus, antiactivators of LuxR-family regulators have evolved multiple times and can operate through distinct mechanisms.…”

Section: Discussionmentioning

confidence: 99%

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

Ramsay

Tester²,

Major³

et al. 2015

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

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Symbiosis islands are integrative and conjugative mobile genetic elements that convert nonsymbiotic rhizobia into nitrogen-fixing symbionts of leguminous plants. Excision of the Mesorhizobium loti symbiosis island ICEMlSym R7A is indirectly activated by quorum sensing through TraR-dependent activation of the excisionase gene rdfS. Here we show that a +1 programmed ribosomal frameshift (PRF) fuses the coding sequences of two TraR-activated genes, msi172 and msi171, producing an activator of rdfS expression named Frameshifted excision activator (FseA). Mass-spectrometry and mutational analyses indicated that the PRF occurred through +1 slippage of the tRNA phe from UUU to UUC within a conserved msi172-encoded motif. FseA activated rdfS expression in the absence of ICEMlSym R7A , suggesting that it directly activated rdfS transcription, despite being unrelated to any characterized DNA-binding proteins. Bacterial two-hybrid and gene-reporter assays demonstrated that FseA was also bound and inhibited by the ICEMlSym R7A -encoded quorum-sensing antiactivator QseM. Thus, activation of ICEMlSym R7A excision is counteracted by TraR antiactivation, ribosomal frameshifting, and FseA antiactivation. This robust suppression likely dampens the inherent biological noise present in the quorum-sensing autoinduction circuit and ensures that ICEMlSym R7A transfer only occurs in a subpopulation of cells in which both qseM expression is repressed and FseA is translated. The architecture of the ICEMlSym R7A transfer regulatory system provides an example of how a set of modular components have assembled through evolution to form a robust genetic toggle that regulates gene transcription and translation at both single-cell and cell-population levels.quorum sensing | antiactivator | ribosomal frameshift | ICE | horizontal gene transfer

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Section: Discussionmentioning

confidence: 99%

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

Ramsay

Tester²,

Major³

et al. 2015

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

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“…A third protein, QslA (PA1244), acts as a potent anti-activator of LasR through heterotrimer formation that can even dissociate previously formed LasR-DNA complexes (Seet and Zhang, 2011 ). This effect is achieved through direct binding of QslA to the ligand-binding-domain (LBD) of LasR in a 2:1 ratio, obscuring the dimerization interface and thereby preventing activation (Fan et al, 2013 ).…”

Section: Introductionmentioning

confidence: 99%

“…Gupta and Schuster found that mutations in either qteE or qscR can produce virtually identical phenotypes under certain conditions (Gupta and Schuster, 2013 ). QteE, QscR, and QslA are not homologous and may bind R-proteins differently (Siehnel et al, 2010 ; Lintz et al, 2011 ; Fan et al, 2013 ). In consideration of this evidence together, several important open questions remain.…”

Section: Introductionmentioning

confidence: 99%

Additive Effects of Quorum Sensing Anti-Activators on Pseudomonas aeruginosa Virulence Traits and Transcriptome

Asfahl

Schuster

2018

Front. Microbiol.

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In the opportunistic pathogen Pseudomonas aeruginosa, quorum sensing (QS) via acyl-homoserine lactone (AHL) signals coordinates virulence gene expression. AHL signals must reach a critical threshold before enough is bound by cognate regulators LasR and RhlR to drive transcription of target genes. In addition, three anti-activator proteins, QteE, QscR, and QslA, sequester QS regulators to increase the threshold for induction and delay expression of QS target genes. It remains unclear how multiple anti-activators work together to achieve the quorum threshold. Here, we employed a combination of mutational, kinetic, phenotypic, and transcriptomic analysis to examine regulatory effects and interactions of the three distinct anti-activators. We observed combinatorial, additive effects on QS gene expression. As measured by reporter gene fusion, individual deletion of each anti-activator gene increased lasB expression and QS-controlled virulence factor production. Deletion of qslA in combination with the deletion of any other anti-activator gene resulted in the greatest increase and earliest activation of lasB gene expression. Western analysis revealed that relative increases in soluble LasR in anti-activator mutants correlate with increased lasB expression and QS-controlled virulence factor production. RNA-seq of the previously uncharacterized QslA and QteE regulons revealed overlapping, yet distinct groups of differentially expressed genes. Simultaneous inactivation of qteE and qslA had the largest effect on gene expression with 999 genes induced and 798 genes repressed in the double mutant vs. wild-type. We found that LasR and RhlR-activated QS genes formed a subset of the genes induced in the qteE, qslA, and double mutant. The activation of almost all of these QS genes was advanced from stationary phase to log phase in the qteE qslA double mutant. Taken together, our results identify additive effects of anti-activation on QS gene expression, likely via LasR and RhlR, but do not rule out QS-independent effects.

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“…35 Even when bound to its native AHL signal ( N -(3-oxo)-dodecanoyl L-homoserine lactone, OdDHL; Figure 1), only structures of the truncated N-terminal ligand-binding domain LasR have been solved to date. 35–37 Further, there have been only two reported studies of LuxR-type proteins bound to non-native ligands: first, the LasR N-terminal domain bound to triphenyl (TP)-type synthetic activators, 35, 38 and second, full-length CviR (from Chromobacterium violaceum ) bound to three AHLs exhibiting differing degrees of partial agonism (octanoyl L-homoserine lactone, decanoyl L-homoserine lactone, and the “chlorolactone” inhibitor CL). 39 …”

Section: Introductionmentioning

confidence: 99%

Unraveling the contributions of hydrogen-bonding interactions to the activity of native and non-native ligands in the quorum-sensing receptor LasR

et al. 2015

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Quorum sensing (QS) via the synthesis and detection of N-acyl L-homoserine lactone (AHL) signals regulates important pathogenic and mutualistic phenotypes in many bacteria. Over the past two decades, the development of non-native molecules that modulate this cell-cell signaling process has become an active area of research. The majority of these compounds were designed for block binding of the native AHL signal to its cognate LuxR-type receptor, and much effort has focused on LasR in the opportunistic pathogen Pseudomonas aeruginosa. Despite a small set of reported LasR structural data, it remains unclear which polar interactions are most important for either (i) activation of the LasR receptor by its native AHL signal, N-(3-oxo)-dodecanoyl L-homoserine lactone (OdDHL), or (ii) activation or inhibition of LasR by related AHL analogs. Herein, we report our investigations into the activity of OdDHL and five synthetic analogs in wild-type LasR and in nine LasR mutants with modifications to key polar residues in their ligand binding sites. Our results allowed us to rank, for the first time, the relative importance of each LasR:OdDHL hydrogen bond for LasR activation and provide strong evidence for the five synthetic ligands binding LasR in a very similar orientation as OdDHL. By delineating the specific molecular interactions that are important for LasR modulation by AHLs, these findings should aid in the design of new synthetic modulators of LasR (and homologous LuxR-type receptors) with improved potencies and selectivities.

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QsIA disrupts LasR dimerization in antiactivation of bacterial quorum sensing

Cited by 42 publications

References 48 publications

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

Ribosomal frameshifting and dual-target antiactivation restrict quorum-sensing–activated transfer of a mobile genetic element

Additive Effects of Quorum Sensing Anti-Activators on Pseudomonas aeruginosa Virulence Traits and Transcriptome

Unraveling the contributions of hydrogen-bonding interactions to the activity of native and non-native ligands in the quorum-sensing receptor LasR

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