Mo1770 Expression of the Oxys Small Regulatory RNA in Luminal Commensal Escherichia coli Attenuates Experimental Colitis

The biogenesis of the essential precursor of the bacterial cell envelope, glucosamine-6-phosphate (GlcN6P), is controlled through intricate post-transcription networks mediated by GlmZ, a small regulatory RNA (sRNA). GlmZ stimulates translation of the mRNA encoding GlcN6P synthetase in Escherichia coli, but when bound by the protein RapZ, it becomes inactivated through cleavage by the endoribonuclease RNase E. Here we report the cryoEM structure of the RapZ:GlmZ complex, revealing a complementary match of the protein tetrameric quaternary structure to an imperfect structural repeat in the RNA. The RNA is contacted mostly through a highly conserved domain of RapZ that shares deep evolutionary relationship with phosphofructokinase and suggests links between metabolism and riboregulation. We also present the structure of a pre-cleavage encounter intermediate formed between the binary RapZ:GlmZ complex and RNase E that reveals how GlmZ is presented and recognised for cleavage. The structures suggest how other encounter complexes might guide recognition and action of endoribonucleases on target transcripts, and how structured substrates in polycistronic precursors are recognised for processing.

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Constitutive Activation of the Escherichia coli Pho Regulon Upregulates rpoS Translation in an Hfq-Dependent Fashion

Journal of Bacteriology ◽

10.1128/jb.185.20.5984-5992.2003 ◽

2003 ◽

Vol 185 (20) ◽

pp. 5984-5992 ◽

Cited By ~ 47

Author(s):

Natividad Ruiz ◽

Thomas J. Silhavy

Keyword(s):

Escherichia Coli ◽

Exponential Growth ◽

Pho Regulon ◽

Regulatory Rna ◽

Genetic Screens ◽

Two Component System ◽

Component System ◽

Small Regulatory Rna ◽

Two Component ◽

Σ Factor

ABSTRACT Regulation of the σ factor RpoS occurs at the levels of transcription, translation, and protein stability activity, and it determines whether Escherichia coli turns on or off the stationary-phase response. To better understand the regulation of RpoS, we conducted genetic screens and found that mutations in the pst locus cause accumulation of RpoS during exponential growth. The pst locus encodes for the components of the high-affinity transport system for inorganic phosphate (Pi), which is involved in sensing Pi levels in the environment. When the Pst transporter is compromised (either by mutation or by Pi starvation), the two-component system PhoBR activates the transcription of the Pho regulon, a subset of genes that encode proteins for transporting and metabolizing alternative phosphate sources. Our data show that strains carrying mutations which constitutively activate the Pho regulon have increased rpoS translation during exponential growth. This upregulation of rpoS translation is Hfq dependent, suggesting the involvement of a small regulatory RNA (sRNA). The transcription of this yet-to-be-identified sRNA is regulated by the PhoBR two-component system.

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