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- David Cabrer-Panes, Juan, et al.
(författare)
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ppGppmediates the growth phase-dependent regulation ofagn43, a phase variable gene, by stimulating its promoter activity
- 2020
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Ingår i: Environmental Microbiology Reports. - : John Wiley & Sons. - 1758-2229. ; 12:4, s. 444-453
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Tidskriftsartikel (refereegranskat)abstract
- Antigen 43 (Ag43) is a self-recognizing outer membrane protein ofEscherichia coliexpressed during intracellular growth and biofilm formation, suggesting a role in infection. The expression ofagn43is under phase variation control, meaning that there are regulatory mechanisms adjusting the percentage ofagn43-expressing cells in the population, in addition to mechanisms modulating the transcriptional expression level in each expressing cell. Phenotypic and transcriptional studies indicate that Ag43 expression is induced upon entry into the stationary phase in a ppGpp-dependent and RpoS-independent manner. The use of single-cell approaches and phase variation deficient strains let to conclude that ppGpp stimulatesagn43promoter activity, rather than affecting the percentage ofagn43-expressing cells. The data highlight the relevance that promoter activity regulation may have, without any involvement of the phase variation state, in the final Ag43 expression output. Theagn43promoter of the MG1655 strain carries an AT-rich discriminator between positions -10 and +1, which is highly conserved among theagn43genes present in the different pathotypes ofE. coli. Remarkably, the AT-rich discriminator is required for the positive transcriptional control mediated by ppGpp.
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| 2. |
- Fernández-Vázquez, Jorge, et al.
(författare)
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ppGpp, the general stress response alarmone, is required for the expression of the α-Hemolysin toxin in the uropathogenic Escherichia coli isolate, J96
- 2022
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Ingår i: International Journal of Molecular Sciences. - : MDPI. - 1661-6596 .- 1422-0067. ; 23:20
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Tidskriftsartikel (refereegranskat)abstract
- ppGpp is an intracellular sensor that, in response to different types of stress, coordinates the rearrangement of the gene expression pattern of bacteria to promote adaptation and survival to new environmental conditions. First described to modulate metabolic adaptive responses, ppGpp modulates the expression of genes belonging to very diverse functional categories. In Escherichia coli, ppGpp regulates the expression of cellular factors that are important during urinary tract infections. Here, we characterize the role of this alarmone in the regulation of the hlyCABDII operon of the UPEC isolate J96, encoding the toxin α-hemolysin that induces cytotoxicity during infection of bladder epithelial cells. ppGpp is required for the expression of the α-hemolysin encoded in hlyCABDII by stimulating its transcriptional expression. Prototrophy suppressor mutations in a ppGpp-deficient strain restore the α-hemolysin expression from this operon to wild-type levels, confirming the requirement of ppGpp for its expression. ppGpp stimulates hlyCABDII expression independently of RpoS, RfaH, Zur, and H-NS. The expression of hlyCABDII is promoted at 37 °C and at low osmolarity. ppGpp is required for the thermoregulation but not for the osmoregulation of the hlyCABDII operon. Studies in both commensal and UPEC isolates demonstrate that no UPEC specific factor is strictly required for the ppGpp-mediated regulation described. Our data further support the role of ppGpp participating in the coordinated regulation of the expression of bacterial factors required during infection.
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