Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

Pannuri, Archana; Yakhnin, Helen; Vakulskas, Christopher A.; Edwards, Adrianne N.; Babitzke, Paul; Romeo, Tony

doi:10.1128/jb.06209-11

Cited by 59 publications

(75 citation statements)

References 66 publications

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“…By inference, products of carbon metabolism downregulate CsrA activity and glycolytic flux through the Embeden-Meyerhof-Parnas pathway, while they activate gluconeogenesis, glycogen synthesis, synthesis of the biofilm exopolysaccharide dPNAG, and pathways and processes favoring stress resistance and survival, which are repressed by CsrA (Fig. 10) (7,17,18,22,24,33).…”

Section: Discussionmentioning

confidence: 99%

“…In Escherichia coli, CsrA activates glycolysis and central carbon pathways (7)(8)(9)(10)(11)(12)(13) and motility (14,15). Conversely, it represses gluconeogenesis (7), glycogen biosynthesis (16)(17)(18)(19)(20), biofilm formation (21)(22)(23)(24), the stringent response (25), and expression of genes involved in other stress resistance and stationary-phase processes, e.g., cstA, hfq, cel, sdiA, and nhaR (24,(26)(27)(28)(29)(30). Its effects on pathogenesis are complex.…”

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Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

et al. 2016

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Cyclic AMP (cAMP) and the cAMP receptor protein (cAMP-CRP) and CsrA are the principal regulators of the catabolite repression and carbon storage global regulatory systems, respectively. cAMP-CRP controls the transcription of genes for carbohydrate metabolism and other processes in response to carbon nutritional status, while CsrA binds to diverse mRNAs and regulates translation, RNA stability, and/or transcription elongation. CsrA also binds to the regulatory small RNAs (sRNAs) CsrB and CsrC, which antagonize its activity. The BarA-UvrY two-component signal transduction system (TCS) directly activates csrB and csrC (csrB/C) transcription, while CsrA does so indirectly. We show that cAMP-CRP inhibits csrB/C transcription without negatively regulating phosphorylated UvrY (P-UvrY) or CsrA levels. A crp deletion caused an elevation in CsrB/C levels in the stationary phase of growth and increased the expression of csrB-lacZ and csrClacZ transcriptional fusions, although modest stimulation of CsrB/C turnover by the crp deletion partially masked the former effects. DNase I footprinting and other studies demonstrated that cAMP-CRP bound specifically to three sites located upstream from the csrC promoter, two of which overlapped the P-UvrY binding site. These two proteins competed for binding at the overlapping sites. In vitro transcription-translation experiments confirmed direct repression of csrC-lacZ expression by cAMP-CRP. In contrast, cAMP-CRP effects on csrB transcription may be mediated indirectly, as it bound nonspecifically to csrB DNA. In the reciprocal direction, CsrA bound to crp mRNA with high affinity and specificity and yet exhibited only modest, conditional effects on expression. Our findings are incorporated into an emerging model for the response of Csr circuitry to carbon nutritional status. IMPORTANCECsr (Rsm) noncoding small RNAs (sRNAs) CsrB and CsrC of Escherichia coli use molecular mimicry to sequester the RNA binding protein CsrA (RsmA) away from lower-affinity mRNA targets, thus eliciting major shifts in the bacterial lifestyle. CsrB/C transcription and turnover are activated by carbon metabolism products (e.g., formate and acetate) and by a preferred carbon source (glucose), respectively. We show that cAMP-CRP, a mediator of classical catabolite repression, inhibits csrC transcription by binding to the upstream region of this gene and also inhibits csrB transcription, apparently indirectly. We propose that glucose availability activates pathways for both synthesis and turnover of CsrB/C, thus shaping the dynamics of global signaling in response to the nutritional environment by poising CsrB/C sRNA levels for rapid response.T he Csr (carbon storage regulator) or Rsm (repressor of stationary-phase metabolites) system is a widely conserved bacterial posttranscriptional regulatory system (1-3). Its components, their functions, and the mechanisms by which the central regulator of this system, CsrA or RsmA, affects gene expression have been studied primarily in Gammaproteobacteria (4-6). The...

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Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

et al. 2016

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“…In the case of flhDC mRNA, which is required for flagellum biosynthesis, binding of CsrA to the leader of flhDC stabilizes the respective mRNA, with overexpression of csrA resulting in increased motility (164). In addition, CsrA functions as a translational repressor capable of destabilizing mRNA transcripts, such as those associated with glycogen and PGA synthesis (6,135) as well as those encoding NhaR, the transcriptional regulator involved in pga operon expression (128). CsrA is antagonized by the small regulatory RNAs (sRNAs) CsrB and CsrC, which are transcriptionally modulated by the membrane-bound TCS BarA/UvrY.…”

Section: Noncoding Rnas Mattermentioning

confidence: 99%

Sticky Situations: Key Components That Control Bacterial Surface Attachment

Petrova

Sauer

2012

Journal of Bacteriology

323

251

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“…The expression of the E. coli pgaABCD operon is tightly regulated. For example, the RNA-binding protein CsrA (carbon storage regulator A) negatively regulates pgaA translation, pgaABCD transcription, and mRNA stability (16,26,27 29 solved the crystal structure of AlgK. In combination with functional analyses, they proposed a mechanism for alginate secretion across the bacterial outer membrane; Little et al (23,24) reported the crystal structures of PgaB and its complex with ␤-1,6-(GlcNAc) 6 and disclosed the catalytic mechanism of the N-deacetylase PgaB on PNAG polymers and the manner of periplasmic translocation of PNAG.…”

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confidence: 99%

“…Quantitative Biofilm Assay-The wild-type E. coli strain MG1655 (MG) produces little or no biofilm because under laboratory conditions, the RNA-binding protein negatively regulates pgaA translation, pgaABCD transcription, and mRNA stability (16,26,27). MG_csrA::kan_⌬pgaA strains (E. coli strain MG1655 with both genes csrA and pgaA disrupted) were transformed with the pgaA expression plasmid.…”

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Structural Basis for Translocation of a Biofilm-supporting Exopolysaccharide across the Bacterial Outer Membrane

Wang

Pannuri

et al. 2016

Journal of Biological Chemistry

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The partially de-N-acetylated poly-␤-1,6-N-acetyl-D-glucosamine (dPNAG) polymer serves as an intercellular biofilm adhesin that plays an essential role for the development and maintenance of integrity of biofilms of diverse bacterial species. Translocation of dPNAG across the bacterial outer membrane is mediated by a tetratricopeptide repeat-containing outer membrane protein, PgaA. To understand the molecular basis of dPNAG translocation, we determined the crystal structure of the C-terminal transmembrane domain of PgaA (residues 513-807). The structure reveals that PgaA forms a 16-strand transmembrane ␤-barrel, closed by four loops on the extracellular surface. Half of the interior surface of the barrel that lies parallel to the translocation pathway is electronegative, suggesting that the corresponding negatively charged residues may assist the secretion of the positively charged dPNAG polymer. In vivo complementation assays in a pgaA deletion bacterial strain showed that a cluster of negatively charged residues proximal to the periplasm is necessary for biofilm formation. Biochemical analyses further revealed that the tetratricopeptide repeat domain of PgaA binds directly to the N-deacetylase PgaB and is critical for biofilm formation. Our studies support a model in which the positively charged PgaB-bound dPNAG polymer is delivered to PgaA through the PgaA-PgaB interaction and is further targeted to the ␤-barrel lumen of PgaA potentially via a charge complementarity mechanism, thus priming the translocation of dPNAG across the bacterial outer membrane.

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Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA

Cited by 59 publications

References 66 publications

Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

Circuitry Linking the Catabolite Repression and Csr Global Regulatory Systems of Escherichia coli

Sticky Situations: Key Components That Control Bacterial Surface Attachment

Structural Basis for Translocation of a Biofilm-supporting Exopolysaccharide across the Bacterial Outer Membrane

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