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Translational Repression of NhaR, a Novel Pathway for Multi-Tier Regulation of Biofilm Circuitry by CsrA
- Source :
- Journal of Bacteriology. 194:79-89
- Publication Year :
- 2011
- Publisher :
- American Society for Microbiology, 2011.
-
Abstract
- The RNA binding protein CsrA (RsmA) represses biofilm formation in several proteobacterial species. In Escherichia coli, it represses the production of the polysaccharide adhesin poly-β-1,6-N-acetyl-d-glucosamine (PGA) by binding to the pgaABCD mRNA leader, inhibiting pgaA translation, and destabilizing this transcript. In addition, CsrA represses genes responsible for the synthesis of cyclic di-GMP, an activator of PGA production. Here we determined that CsrA also represses NhaR, a LysR-type transcriptional regulator which responds to elevated [Na+] and alkaline pH and activates the transcription of the pgaABCD operon. Gel shift studies revealed that CsrA binds at two sites in the 5′ untranslated segment of nhaR, one of which overlaps the Shine-Dalgarno sequence. An epitope-tagged NhaR protein, expressed from the nhaR chromosomal locus, and an nhaR posttranscriptional reporter fusion (PlacUV5-nhaR′-′lacZ) both showed robust repression by CsrA. Northern blotting revealed a complex transcription pattern for the nhaAR locus. Nevertheless, CsrA did not repress nhaR mRNA levels. Toeprinting assays showed that CsrA competes effectively with the ribosome for binding to the translation initiation region of nhaR. Together, these findings indicate that CsrA blocks nhaR translation. Epistasis studies with a pgaA-lacZ transcriptional fusion confirmed a model in which CsrA indirectly represses pgaABCD transcription via NhaR. We conclude that CsrA regulates the horizontally acquired pgaABCD operon and PGA biosynthesis at multiple levels. Furthermore, nhaR repression exemplifies an expanding role for CsrA as a global regulator of stress response systems.
- Subjects :
- beta-Glucans
Operon
Down-Regulation
Porins
lac operon
RNA-binding protein
Biology
Microbiology
Eukaryotic translation
Transcription (biology)
Escherichia coli
Transcriptional regulation
RNA, Messenger
Cyclic GMP
Molecular Biology
Psychological repression
Activator (genetics)
Escherichia coli Proteins
Sodium
RNA-Binding Proteins
Gene Expression Regulation, Bacterial
Articles
Hydrogen-Ion Concentration
Molecular biology
DNA-Binding Proteins
Repressor Proteins
Biofilms
Protein Biosynthesis
Transcription Factors
Subjects
Details
- ISSN :
- 00219193
- Volume :
- 194
- Database :
- OpenAIRE
- Journal :
- Journal of Bacteriology
- Accession number :
- edsair.doi.dedup.....fa02514cc045fd0e1c684dd735817994