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Superfolder GFP reporters validate diverse new mRNA targets of the classic porin regulator, MicF RNA

ABSTRACT: MicF is a textbook example of a small regulatory RNA (sRNA) that acts on a trans-encoded target mRNA through imperfect base paring. The discovery of MicF as a post-transcriptional repressor of the major Escherichia coli porin OmpF established the paradigm for a meanwhile common mechanism of translational inhibition, through antisense sequestration of a ribosome binding site. However, whether MicF regulates additional genes has remained unknown for almost three decades. Here, we have harnessed the novel superfolder variant of GFP for reporter-gene fusions to validate newly predicted targets of MicF in Salmonella. We show that the conserved 5’ end of MicF acts by seed pairing to repress the mRNAs of global transcriptional regulator Lrp, periplasmic protein YahO, and lipid A-modifying enzyme LpxR. Whilst MicF binds lrp and yahO in the 5’ UTR, it targets lpxR at both the ribosome binding site and deep within the coding sequence. Repression in the coding sequence of lpxR may be achieved by decreasing mRNA stability through exacerbating the use of a native RNase E site proximal to the short MicF-lpxR duplex. Altogether, this study assigns the classic MicF sRNA to the growing class of Hfqassociated regulators that use diverse mechanisms to impact multiple loci.

ORGANISM(S): Salmonella enterica Salmonella enterica subsp. enterica serovar Typhimurium str. SL1344

PROVIDER: GSE35848 | GEO | 2012/02/17

SECONDARY ACCESSION(S): PRJNA151865

REPOSITORIES: GEO

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Superfolder GFP reporters validate diverse new mRNA targets of the classic porin regulator, MicF RNA

Project description:MicF is a textbook example of a small regulatory RNA (sRNA) that acts on a trans-encoded target mRNA through imperfect base paring. The discovery of MicF as a post-transcriptional repressor of the major Escherichia coli porin OmpF established the paradigm for a meanwhile common mechanism of translational inhibition, through antisense sequestration of a ribosome binding site. However, whether MicF regulates additional genes has remained unknown for almost three decades. Here, we have harnessed the novel superfolder variant of GFP for reporter-gene fusions to validate newly predicted targets of MicF in Salmonella. We show that the conserved 5’ end of MicF acts by seed pairing to repress the mRNAs of global transcriptional regulator Lrp, periplasmic protein YahO, and lipid A-modifying enzyme LpxR. Whilst MicF binds lrp and yahO in the 5’ UTR, it targets lpxR at both the ribosome binding site and deep within the coding sequence. Repression in the coding sequence of lpxR may be achieved by decreasing mRNA stability through exacerbating the use of a native RNase E site proximal to the short MicF-lpxR duplex. Altogether, this study assigns the classic MicF sRNA to the growing class of Hfqassociated regulators that use diverse mechanisms to impact multiple loci. To determine the targets of the small regulatory RNA MicF in S. Typhimurium, we looked at the effect of a short pulse of MicF over-expression on the Salmonella transcriptome. To achieve over-expression, the micF gene was cloned in the pBAD plasmid and induced with 0.2% L-arabinose for 10 min. We then extracted the total RNA for transcriptional profiling. A strain carrying the pBAD plasmid w/o insert was used as negative control (also induced by L-arabinose). 3 biological replicates were performed. This sRNA target identification strategy has been described in Papenfort et al; Molecular Microbiology (2006) 62(6), 1674?1688.

2012-02-17 | E-GEOD-35848 | biostudies-arrayexpress

Neisseria meningitides small RNA's regulate Citric acid cycle activity under Feast and Famine conditions

Project description:We identified twin small non-coding RNAs regulating tricarboxylic acid (TCA) cycle activity in Neisseria meningitidis. Expression of TCA cycle enzymes was elevated in sRNA deletion mutants. Direct interaction between sRNAs and the ribosomal entry sites on target mRNAs was demonstrated. Expression of the sRNAs was down-regulated in cells grown in poor medium with glucose as the sole carbon source but not without lrp, indicating that sRNA expression is controlled by the stringent response. N. meningitidis, over-expressing the sRNAs replicated in blood, but not in human cerebrospinal fluid. In addition, Lrp synthesis was inhibited by direct interaction between the sRNA and the 5’ UTR of lrp. sRNAs control adaptation of N. meningitidis to variation in nutrient supply in different niches of its host.

2017-03-22 | PXD000891 | Pride

Escherichia coli Lrp regulates one-third of the genome via direct, cooperative, and indirect paths

Project description:The global regulator Lrp plays a crucial role in regulating metabolism, virulence and motility in response to environmental conditions. Lrp has previously been shown to activate or repress approximately 10% of genes in Escherichia coli. However, the full spectrum of targets, and how Lrp acts to regulate them, has stymied earlier study. We have combined matched ChIP-seq and RNA sequencing under nine physiological conditions to map the binding and regulatory activity of Lrp as it directs responses to nutrient abundance. In addition to identifying hundreds of novel Lrp targets, we observe two new global trends: first, that Lrp will often bind to promoters in a poised position under conditions when it has no regulatory activity, and second, that nutrient levels induce a global shift in the equilibrium between non-specific and sequence-specific DNA binding. The overall regulatory behavior of Lrp, which as we now show regulates 35% of E. coli genes directly or indirectly under at least one condition, thus arises from the interaction between changes in Lrp binding specificity and cooperative action with other regulators.

2018-11-28 | GSE111874 | GEO

Bi-directional ribosome scanning controls the stringency of start codon selection

Project description:The fidelity of start codon recognition by ribosomes is paramount during protein synthesis. The textbook knowledge of eukaryotic translation initiation depicts 5’→3’ unidirectional migration of the pre-initiation complex (PIC) along the 5’UTR. In probing translation initiation from ultra-short 5’UTR, we report that an AUG triplet near the 5’ end can be selected via PIC backsliding. The bi-directional ribosome scanning is supported by competitive selection of closely spaced AUG codons and recognition of two initiation sites flanking an internal ribosome entry site. Transcriptome-wide PIC profiling reveals footprints with an oscillation pattern near the 5’ end and start codons. Depleting the RNA helicase eIF4A leads to reduced PIC oscillations and impaired selection of 5’ end start codons. Enhancing the ATPase activity of eIF4A promotes nonlinear PIC scanning and stimulates upstream translation initiation. The helicase-mediated PIC conformational switch may provide an operational mechanism that unifies ribosome recruitment, scanning, and start codon selection.

2021-11-24 | GSE176058 | GEO

New RoxS sRNA targets identified in B. subtilis by pulsed SILAC

Project description:Non-coding RNA (sRNA) are playing a key role in gene expression in bacteria. In general, sRNA regulates gene expression by base-pairing with ribosome binding sites to block translation. The modification of the ribosome trafficking generally affects mRNA stability. However, few examples have been described in bacteria where sRNA binding are mainly affected translation without modifying mRNA stability. In order to identify such targets in B. subtilis, we developed a pulsed-SILAC method allowing to label new protein synthesis after a short expression of the sRNA. We applied it to the best characterized sRNA in this bacteria, namely RoxS. RoxS sRNA was previously shown to interfere with the expression of genes encoding enzymes of the central metabolism to control the NAD/NADH ratio in B. subtilis.

2023-01-18 | MSV000091084 | MassIVE

Inter-domain dynamics in the chaperone SurA and multi-site binding to its unfolded outer membrane protein clients revealed by HDX-MS

Project description:We present HDX-MS data of apo-SurA, SurA in complex with OmpX, OmpF and a peptide with sequence WEYIPNV to define (1) interdomain dynamics in the periplasmic chaperone SurA, and (2) the binding site of OmpX, OmpF and WEYIPNV on SurA.

2020-05-22 | PXD017010 | Pride

The sRNA SorY confers resistance during photooxidative stress by affecting a metabolite transporter in Rhodobacter sphaeroides

Project description:Exposure to oxygen and light generates photooxidative stress by the bacteriochlorophyll a mediated formation of singlet oxygen (1O2) in the facultative photosynthetic bacterium Rhodobacter sphaeroides. We have identified SorY as an sRNA, which is induced under several stress conditions and confers increased resistance against 1O2. SorY by direct interaction decreases the levels of takP mRNA, encoding a TRAP-T transporter. A takP mutant shows higher resistance to 1O2 than the wild type, which is no longer affected by SorY. We present a model in which SorY reduces the metabolite flux into the TCA cycle by reducing malate import through TakP. It was previously shown that oxidative stress in bacteria leads to switch from glycolysis to the pentose phosphate cycle and to reduced activity of the tricaboxylic acid cycle. As a consequence the production of the prooxidant NADH is reduced and production of the protective NADPH is enhanced. In R. sphaeroides enzymes for glycolysis, pentose phosphate pathway, EntnerM-bM-^@M-^SDoudoroff pathway and gluconeogenesis are induced in response to 1O2 by the alternative sigma factor RpoHII. The same is true for the sRNA SorY. By limiting malate import SorY thus contributes to the balance of the metabolic fluxes under photooxidative stress conditions. This assigns a so far unknown function to an sRNA in oxidative stress response. RNA samples collected from a control strain harbouring an empty vector (2.4.1pBBR) and of the SorY overexpressing strain (2.4.1pBBRSorYi) after 10 min of 1O2 stress were analyzed by two-color microarrays

2014-11-18 | E-GEOD-63328 | biostudies-arrayexpress

Phenotypic and transcriptional analysis of the osmotic regulator OmpR in Yersinia pestis

Project description:Background The osmotic regulator OmpR in Escherichia coli regulates differentially the expression of major porin proteins OmpF and OmpC. In Yersinia enterocolitica and Y. pseudotuberculosis, OmpR is required for both virulence and survival within macrophages. However, the phenotypic and regulatory roles of OmpR in Y. pestis are not yet fully understood. Results Y. pestis OmpR is involved in building resistance against phagocytosis and controls the adaptation to various stressful conditions met in macrophages. The ompR mutation likely did not affect the virulence of Y. pestis strain 201 that was a human-avirulent enzootic strain. The microarray-based comparative transcriptome analysis disclosed a set of 224 genes whose expressions were affected by the ompR mutation, indicating the global regulatory role of OmpR in Y. pestis. Real-time RT-PCR or lacZ fusion reporter assay further validated 16 OmpR-dependent genes, for which OmpR consensus-like sequences were found within their upstream DNA regions. ompC, F, X, and R were up-regulated dramatically with the increase of medium osmolarity, which was mediated by OmpR occupying the target promoter regions in a tandem manner. Conclusion OmpR contributes to the resistance against phagocytosis or survival within macrophages, which is conserved in the pathogenic yersiniae. Y. pestis OmpR regulates ompC, F, X, and R directly through OmpR-promoter DNA association. There is an inducible expressions of the pore-forming proteins OmpF, C, and X at high osmolarity in Y. pestis, in contrast to the reciprocal regulation of them in E. coli. The main difference is that ompF expression is not repressed at high osmolarity in Y. pestis, which is likely due to the absence of a promoter-distal OmpR-binding site for ompF.

2011-10-24 | GSE26601 | GEO

High throughput analysis of binding of E. coli Lrp mutants

Project description:Feast-Famine Response Proteins are a widely conserved class of global regulators in prokaryotes, the most highly studied of which is the E. coli leucine-responsive regulatory protein (Lrp). Lrp senses environmental nutrition status and subsequently regulates up to one-third of the genes in E. coli, either directly or indirectly. Lrp exists predominantly as octamers and hexadecamers (16mers), where leucine is believed to shift the equilibrium towards the octameric state. In this study, we analyzed the effects of three oligomerization state mutants of Lrp in terms of their ability to bind to DNA and regulate gene expression in response to exogenous leucine. We find that oligomerization beyond dimers is required for Lrp’s regulatory activity, and that contrary to prior speculation, exogenous leucine modulates Lrp activity at its target promoters exclusively by inhibiting Lrp binding to DNA. We also find evidence that Lrp binding bridges DNA over length scales of multiple kilobases, revealing a new range of mechanisms for Lrp-mediated transcriptional regulation.

2023-01-31 | GSE198120 | GEO

The sRNA SorY confers resistance during photooxidative stress by affecting a metabolite transporter in Rhodobacter sphaeroides

Project description:Exposure to oxygen and light generates photooxidative stress by the bacteriochlorophyll a mediated formation of singlet oxygen (1O2) in the facultative photosynthetic bacterium Rhodobacter sphaeroides. We have identified SorY as an sRNA, which is induced under several stress conditions and confers increased resistance against 1O2. SorY by direct interaction decreases the levels of takP mRNA, encoding a TRAP-T transporter. A takP mutant shows higher resistance to 1O2 than the wild type, which is no longer affected by SorY. We present a model in which SorY reduces the metabolite flux into the TCA cycle by reducing malate import through TakP. It was previously shown that oxidative stress in bacteria leads to switch from glycolysis to the pentose phosphate cycle and to reduced activity of the tricaboxylic acid cycle. As a consequence the production of the prooxidant NADH is reduced and production of the protective NADPH is enhanced. In R. sphaeroides enzymes for glycolysis, pentose phosphate pathway, Entner–Doudoroff pathway and gluconeogenesis are induced in response to 1O2 by the alternative sigma factor RpoHII. The same is true for the sRNA SorY. By limiting malate import SorY thus contributes to the balance of the metabolic fluxes under photooxidative stress conditions. This assigns a so far unknown function to an sRNA in oxidative stress response.

2014-11-18 | GSE63328 | GEO

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