Silencing of DNase Colicin E8 Gene Expression by a Complex Nucleoprotein Assembly Ensures Timely Colicin Induction


Colicins are plasmid-encoded narrow spectrum antibiotics that are synthesized by strains of Escherichia coli and govern intraspecies competition. In a previous report, we demonstrated that the global transcriptional factor IscR, co dependently with the master regulator of the DNA damage response, LexA, delays induction of the pore forming colicin genes after SOS induction. Here we show that IscR is not involved in the regulation of nuclease colicins, but that the AsnC protein is. We report that AsnC, in concert with LexA, is the key controller of the temporal induction of the DNA degrading colicin E8 gene (cea8), after DNA damage. We demonstrate that a large AsnC nucleosome-like structure, in conjunction with two LexA molecules, prevent cea8 transcription initiation and that AsnC binding activity is directly modulated by L asparagine. We show that L-asparagine is an environmental factor that has a marked impact on cea8 promoter regulation. Our results show that AsnC also modulates the expression of several other DNase and RNase colicin genes but does not substantially affect pore-forming colicin K gene expression. We propose that selection pressure has "chosen" highly conserved regulators to control colicin expression in E. coli strains, enabling similar colicin gene silencing among bacteria upon exchange of colicinogenic plasmids.

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Divisions: College of Health & Life Sciences > School of Biosciences
Additional Information: © 2015 Kamenšek et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited Funding: DFB was supported by BBSRC grant BB/J006076/1 (, awarded to both DFB and SJWB. SK was supported by grant from the Slovenian Research Agency (J3-3624) ( ZP and DŽB were supported by grant from the Slovenian Research Agency (P1-0198). MB was supported by grant from the Slovenian Research Agency (P1-0207).
Uncontrolled Keywords: Asparagine/metabolism,Bacterial Proteins/genetics,Colicins/genetics,Escherichia coli/genetics,Escherichia coli Proteins/genetics,Gene Expression Regulation, Bacterial,Nucleoproteins/genetics,Promoter Regions, Genetic,SOS Response, Genetics,Serine Endopeptidases/genetics,Trans-Activators/genetics,Transcription Factors/genetics
Publication ISSN: 1553-7404
Last Modified: 15 Jul 2024 08:15
Date Deposited: 18 Jan 2022 13:54
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Related URLs: https://journal ... al.pgen.1005354 (Publisher URL)
PURE Output Type: Article
Published Date: 2015-06-26
Authors: Kamenšek, Simona
Browning, Douglas F (ORCID Profile 0000-0003-4672-3514)
Podlesek, Zdravko
Busby, Stephen J W
Žgur-Bertok, Darja
Butala, Matej



Version: Published Version

License: Creative Commons Attribution

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