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Journal of Bacteriology, February 2009, p. 762-772, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01331-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Influence of Operator Site Geometry on Transcriptional Control by the YefM-YoeB Toxin-Antitoxin Complex{triangledown}

Simon E. S. Bailey{dagger} and Finbarr Hayes*

Faculty of Life Sciences and Manchester Interdisciplinary Biocentre, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom

Received 23 September 2008/ Accepted 9 November 2008

YefM-YoeB is among the most prevalent and well-characterized toxin-antitoxin complexes. YoeB toxin is an endoribonuclease whose activity is inhibited by YefM antitoxin. The regions 5' of yefM-yoeB in diverse bacteria possess conserved sequence motifs that mediate transcriptional autorepression. The yefM-yoeB operator site arrangement is exemplified in Escherichia coli: a pair of palindromes with core hexamer motifs and a center-to-center distance of 12 bp overlap the yefM-yoeB promoter. YefM is an autorepressor that initially recognizes a long palindrome containing the core hexamer, followed by binding to a short repeat. YoeB corepressor greatly enhances the YefM-operator interaction. Scanning mutagenesis demonstrated that the short repeat is crucial for correct interaction of YefM-YoeB with the operator site in vivo and in vitro. Moreover, altering the relative positions of the two palindromes on the DNA helix abrogated YefM-YoeB cooperative interactions with the repeats: complex binding to the long repeat was maintained but was perturbed to the short repeat. Although YefM lacks a canonical DNA binding motif, dual conserved arginine residues embedded in a basic patch of the protein are crucial for operator recognition. Deciphering the molecular basis of toxin-antitoxin transcriptional control will provide key insights into toxin-antitoxin activation and function.

* Corresponding author. Mailing address: Faculty of Life Sciences and Manchester Interdisciplinary Biocentre, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom. Phone: 44 161 3068934. Fax: 44 161 3065201. E-mail: finbarr.hayes{at}manchester.ac.uk

{triangledown} Published ahead of print on 21 November 2008.

{dagger} Present address: IC Consultants, Ltd., 58 Prince's Gate, Exhibition Road, London SW7 2PG, United Kingdom.

Journal of Bacteriology, February 2009, p. 762-772, Vol. 191, No. 3
0021-9193/09/$08.00+0     doi:10.1128/JB.01331-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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