The Cotranscribed Salmonella enterica sv. Typhi tsx and impX Genes Encode Opposing Nucleoside-Specific Import and Export Proteins

Bucarey, Sergio A.; Villagra, Nicolás A.; Fuentes, Juan A.; Mora, Gabriela

doi:10.1534/genetics.105.054700

Cited by 8 publications

(10 citation statements)

References 40 publications

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“…The hypothesis is that the efflux systems serve as safety valves to prevent the accumulation to toxic levels of the nutrients in question, and this hypothesis has been validated by genetic studies in a number of instances (Vrljic et al 1996;Simic et al 2001;Kennerknecht et al 2002;Kutukova et al 2005;Bucarey et al 2006). One would also expect that the exporters are tightly regulated (Bellmann et al 2001;Trötschel et al 2005), in order to minimize futile cycling of substrate flux across the cell membrane.…”

mentioning

confidence: 99%

Environmental regulation operating at the promoter clearance step of bacterial transcription

Laishram¹,

Gowrishankar²

2007

Genes Dev.

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In vivo transcription of the Escherichia coli argO gene, which encodes an arginine (Arg) exporter, requires the LysR-family regulator protein ArgP (previously called IciA) and is induced in the presence of Arg or its naturally occurring antimetabolite analog canavanine. Lysine (Lys) addition, on the other hand, phenocopies an argP mutation to result in the shutoff of argO expression. We now report that the ArgP dimer by itself is able to bind the argO promoter-operator region to form a binary complex, but that the formation of a ternary complex with RNA polymerase is greatly stimulated only in presence of a coeffector. Both Arg and Lys were proficient as coeffectors for ArgP-mediated recruitment of RNA polymerase to, and open complex formation at, the argO promoter, although only Arg (but not Lys) was competent to activate transcription. The two coeffectors competed for binding to ArgP, and the ternary complex that had been assembled on the argO template in the presence of Lys could be chased into a transcriptionally active state upon Arg addition. Our results support a novel mechanism of argO regulation in which Lys-bound ArgP reversibly restrains RNA polymerase at the promoter, at a step (following open complex formation) that precedes, and is common to, both abortive and productive transcription. This represents, therefore, the first example of an environmental signal regulating the final step of promoter clearance by RNA polymerase in bacterial transcription. We propose that, in E. coli cells, the ternary complex remains assembled and poised at the argO promoter at all times to respond, positively or negatively, to instantaneous changes in the ratio of intracellular Arg to Lys concentrations.[Keywords: ArgP; arginine export; bacterial transcription; gene regulation; promoter clearance] Supplemental material is available at http://www.genesdev.org.

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confidence: 99%

Environmental regulation operating at the promoter clearance step of bacterial transcription

Laishram¹,

Gowrishankar²

2007

Genes Dev.

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“…hlyCABD in E. coli, raxSTAB in Xanthomonas oryzae) (Bielaszewska et al, 2014;Ronald, 2014), supporting the idea that S. Typhi SPI-9 genes could indeed encode a T1SS. Furthermore, other genomic islands are constituted by operons, such as SPI-18 (Faucher et al, 2009;Fuentes et al, 2008), type IV pilus encoded in SPI-7 (Bueno et al, 2004) and tsx-impX (Bucarey et al, 2006) in S. enterica, emphasizing the importance of a concerted regulation of newly acquired functions.…”

Section: Discussionmentioning

confidence: 99%

“…S. Typhi STH2370 STY2875-3xFLAG, S. Typhi STY2876-3xFLAG, S. Typhi STY2877-3XFLAG, S. Typhi STY2878-3xFLAG, S. Typhi ompA-3xFLAG and S. Typhi impX-3xFLAG mutants were constructed using the primers listed in Table 1 as previously described (Uzzau et al, 2001). S. Typhi rpoS-3xFLAG and S. Typhi impX-3xFLAG strains have been previously reported (Bucarey et al, 2006;Fuentes et al, 2009;Jofre et al, 2014). All the double mutants were constructed by electrotransformation with genomic DNA (gDNA) from single mutants as described (Toro et al, 1998).…”

Section: Methodsmentioning

confidence: 99%

“…We were unable to detect STY2875 in the supernatant fraction (data not shown). Immunodetection of epitope-tagged (3xFLAG) proteins OmpA (outer membrane protein), ImpX (inner membrane protein) (Bucarey et al, 2006) and RpoS (cytoplasmic protein) (Jofre et al, 2014), obtained from bacteria cultured to stationary phase (OD 600 =1.4) in LB pH 7.0, was used as control (Fig. 3).…”

Section: Spi-9 Orfs Of S Typhi Sth2370 Are Induced Under Low Ph and mentioning

confidence: 99%

“…Immunodetection of epitope-tagged (3xFLAG) proteins STY2875 (right), STY2876, STY2876, STY2877 and STY2878 (left) on the membrane fraction (MF; outer membrane and inner membrane), and cytoplasmic fraction (CF). Immunodetection of epitope-tagged (3xFLAG) proteins OmpA (outer membrane protein), ImpX (inner membrane protein) (Bucarey et al, 2006) and RpoS (cytoplasmic protein) (Jofre et al, 2014) as fractionation control is shown (right). An additional band of approximately 36 kDA found for RpoS was previously reported (Jofre et al, 2014).…”

Section: Spi-9 Orfs Of S Typhi Sth2370 Are Induced Under Low Ph and mentioning

confidence: 99%

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SPI-9 of Salmonella enterica serovar Typhi is constituted by an operon positively regulated by RpoS and contributes to adherence to epithelial cells in culture

et al. 2016

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The genomic island 9 (SPI-9) from Salmonella enterica serovar Typhi (S. Typhi) carries three ORFs (STY2876, STY2877, STY2878) presenting 98 % identity with a type 1 secretory apparatus (T1SS), and a single ORF (STY2875) similar to a large RTX-like protein exhibiting repeated Ig domains. BapA, the Salmonella enterica serovar Enteritidis orthologous to S. Typhi STY2875, has been associated with biofilm formation, and is described as a virulence factor in mice. Preliminary in silico analyses revealed that S. Typhi STY2875 ORF has a 600 bp deletion compared with S. Enteritidis bapA, suggesting that S. Typhi STY2875 might be non-functional. At present, SPI-9 has not been studied in S. Typhi. We found that the genes constituting SPI-9 are arranged in an operon whose promoter was up-regulated in high osmolarity and low pH in a RpoS-dependent manner. All the proteins encoded by S. Typhi SPI-9 were located at the membrane fraction, consistent with their putative role as T1SS. Furthermore, SPI-9 contributed to adherence of S. Typhi to epithelial cells when bacteria were grown under high osmolarity or low pH. Under the test conditions, S. Typhi SPI-9 did not participate in biofilm formation. SPI-9 is functional in S. Typhi and encodes an adhesin induced under conditions normally found in the intestine, such as high osmolarity. Hence, this is an example of a locus that might be designated a pseudogene by computational approaches but not by direct biological assays.

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The ompW (porin) gene mediates methyl viologen (paraquat) efflux in Salmonella enterica serovar Typhimurium

Gil

Ipinza

Fuentes

et al. 2007

Research in Microbiology

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The Cotranscribed Salmonella enterica sv. Typhi tsx and impX Genes Encode Opposing Nucleoside-Specific Import and Export Proteins

Cited by 8 publications

References 40 publications

Environmental regulation operating at the promoter clearance step of bacterial transcription

Environmental regulation operating at the promoter clearance step of bacterial transcription

SPI-9 of Salmonella enterica serovar Typhi is constituted by an operon positively regulated by RpoS and contributes to adherence to epithelial cells in culture

The ompW (porin) gene mediates methyl viologen (paraquat) efflux in Salmonella enterica serovar Typhimurium

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