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Curr Opin Microbiol. 2015 Feb;23:8-13. doi: 10.1016/j.mib.2014.10.005. Epub 2014 Nov 5.

Integrated circuits: how transcriptional silencing and counter-silencing facilitate bacterial evolution.

Author information

1
Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA.
2
Department of Molecular Genetics, University of Toronto, Toronto, Ontario M5S 1A8, Canada.
3
Department of Laboratory Medicine, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Microbiology, University of Washington School of Medicine, Seattle, WA 98195, USA. Electronic address: fcfang@u.washington.edu.

Abstract

Horizontal gene transfer is a major contributor to bacterial evolution and diversity. For a bacterial cell to utilize newly-acquired traits such as virulence and antibiotic resistance, new genes must be integrated into the existing regulatory circuitry to allow appropriate expression. Xenogeneic silencing of horizontally-acquired genes by H-NS or other nucleoid-associated proteins avoids adventitious expression and can be relieved by other DNA-binding counter-silencing proteins in an environmentally-responsive and physiologically-responsive manner. Biochemical and genetic analyses have recently demonstrated that counter-silencing can occur at a variety of promoter architectures, in contrast to classical transcriptional activation. Disruption of H-NS nucleoprotein filaments by DNA bending is a suggested mechanism by which silencing can be relieved. This review discusses recent advances in our understanding of the mechanisms and importance of xenogeneic silencing and counter-silencing in the successful integration of horizontally-acquired genes into regulatory networks.

PMID:
25461567
PMCID:
PMC4323728
DOI:
10.1016/j.mib.2014.10.005
[Indexed for MEDLINE]
Free PMC Article

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