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Nat Commun. 2014 Oct 28;5:5270. doi: 10.1038/ncomms6270.

Evolutionary expansion of a regulatory network by counter-silencing.

Author information

1
Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA.
2
Department of Chemistry, University of Washington, Seattle, Washington 98195, USA.
3
1] Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, Washington 98195, USA [2] Department of Microbiology, University of Washington School of Medicine, Seattle, Washington 98195, USA.

Abstract

Horizontal gene transfer plays a major role in bacterial evolution. Successful acquisition of new genes requires their incorporation into existing regulatory networks. This study compares the regulation of conserved genes in the PhoPQ regulon of Salmonella enterica serovar Typhimurium with that of PhoPQ-regulated horizontally acquired genes, which are silenced by the histone-like protein H-NS. We demonstrate that PhoP upregulates conserved and horizontally acquired genes by distinct mechanisms. Conserved genes are regulated by classical PhoP-mediated activation and are invariant in promoter architecture, whereas horizontally acquired genes exhibit variable promoter architecture and are regulated by PhoP-mediated counter-silencing. Biochemical analyses show that a horizontally acquired promoter adopts different structures in the silenced and counter-silenced states, implicating the remodelling of the H-NS nucleoprotein filament and the subsequent restoration of open-complex formation as the central mechanism of counter-silencing. Our results indicate that counter-silencing is favoured in the regulatory integration of newly acquired genes because it is able to accommodate multiple promoter architectures.

PMID:
25348042
PMCID:
PMC4215172
DOI:
10.1038/ncomms6270
[Indexed for MEDLINE]
Free PMC Article

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