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A Complex Genetic Switch Involving Overlapping Divergent Promoters and DNA Looping Regulates Expression of Conjugation Genes of a Gram-positive Plasmid

Lookup NU author(s): Dr Ling Juan Wu



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Plasmid conjugation plays a significant role in the dissemination of antibiotic resistance and pathogenicity determinants. Understanding how conjugation is regulated is important to gain insights into these features. Little is known about regulation of conjugation systems present on plasmids from Gram-positive bacteria. pLS20 is a native conjugative plasmid from the Gram-positive bacterium Bacillus subtilis. Recently the key players that repress and activate pLS20 conjugation have been identified. Here we studied in detail the molecular mechanism regulating the pLS20 conjugation genes using both in vivo and in vitro approaches. Our results show that conjugation is subject to the control of a complex genetic switch where at least three levels of regulation are integrated. The first of the three layers involves overlapping divergent promoters of different strengths regulating expression of the conjugation genes and the key transcriptional regulator Rco(LS20). The second layer involves a triple function of Rco(LS20) being a repressor of the main conjugation promoter and an activator and repressor of its own promoter at low and high concentrations, respectively. The third level of regulation concerns formation of a DNA loop mediated by simultaneous binding of tetrameric Rco(LS20) to two operators, one of which overlaps with the divergent promoters. The combination of these three layers of regulation in the same switch allows the main conjugation promoter to be tightly repressed during conditions unfavorable to conjugation while maintaining the sensitivity to accurately switch on the conjugation genes when appropriate conditions occur. The implications of the regulatory switch and comparison with other genetic switches involving DNA looping are discussed.

Publication metadata

Author(s): Ramachandran G, Singh PK, Luque-Ortega JR, Yuste L, Alfonso C, Rojo F, Wu LJ, Meijer WJJ

Publication type: Article

Publication status: Published

Journal: PLOS Genetics

Year: 2014

Volume: 10

Issue: 10

Online publication date: 23/10/2014

Acceptance date: 03/09/2014

Date deposited: 06/03/2015

ISSN (print): 1553-7390

ISSN (electronic): 1553-7404

Publisher: Public Library of Science


DOI: 10.1371/journal.pgen.1004733


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Funder referenceFunder name
Spanish Research Council (CSIC)
098374/Z/12/ZWellcome Trust Investigator Award
BFU2012-32797Spanish Ministry of Economy and Competitiveness
Bio2013-41489-PMinistry of Economy and Competitiveness of the Spanish Government
BFU2008-04034/BMCMinistry of Science and Innovation
BIO2011-28941-CO3Ministry of Science and Innovation