Pervasive transcription enhances the accessibility of H-NS-silenced promoters and generates bistability in Salmonella virulence gene expression - Archive ouverte HAL Accéder directement au contenu
Pré-Publication, Document De Travail Année : 2022

Pervasive transcription enhances the accessibility of H-NS-silenced promoters and generates bistability in Salmonella virulence gene expression

Résumé

Summary In Escherichia coli and Salmonella , many genes silenced by the nucleoid structuring protein H-NS are activated upon inhibiting Rho-dependent transcription termination. This response is poorly understood and difficult to reconcile with the view that H-NS acts mainly by blocking transcription initiation. Here we have analysed the basis for the upregulation of H-NS-silenced Salmonella Pathogenicity Island 1 (SPI-1) in cells depleted of Rho-cofactor NusG. Evidence from genetic experiments, semi-quantitative 5’ RACE-Seq and ChiP-Seq shows that transcription originating from spurious antisense promoters, when not stopped by Rho, elongates into a H-NS-bound regulatory region of SPI-1, displacing H-NS and rendering the DNA accessible to the master regulator HilD. In turn, HilD’s ability to activate its own transcription triggers a positive feedback loop that results in transcriptional activation of the entire SPI-1. Significantly, single-cell analyses revealed that this mechanism is largely responsible for the coexistence of two subpopulations of cells that, although genetically identical, either express or don’t express SPI-1 genes. We propose that cell-to-cell differences produced by stochastic spurious transcription, combined with feedback loops that perpetuate the activated state, can generate bimodal gene expression patterns in bacterial populations.

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Bactériologie
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Dates et versions

hal-03850231 , version 1 (13-11-2022)

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Nara Figueroa-Bossi, María Antonia Sanchez-Romero, Patricia Kerboriou, Delphine Naquin, Clara Mendes, et al.. Pervasive transcription enhances the accessibility of H-NS-silenced promoters and generates bistability in Salmonella virulence gene expression. 2022. ⟨hal-03850231⟩
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