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Interactions of the Antizyme AtoC with Regulatory Elements of the Escherichia coli atoDAEB Operon

Meropi K. Matta,¹ Efthimia E. Lioliou,^2, Cynthia H. Panagiotidis,¹ Dimitrios A. Kyriakidis,^2,3 and Christos A. Panagiotidis^1*

Department of Pharmaceutical Sciences,¹ Laboratory of Biochemistry, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki 54124,² National Hellenic Research Foundation, 48 Vas. Constantinou, Athens 11636, Greece³

Received 8 February 2007/ Accepted 21 June 2007

AtoC has a dual function as both an antizyme, the posttranslational inhibitor of polyamine biosynthetic enzymes, and the transcriptional regulator of genes involved in short-chain fatty acid catabolism (the atoDAEB operon). We have previously shown that AtoC is the response regulator of the AtoS-AtoC two-component signal transduction system that activates atoDAEB when Escherichia coli is exposed to acetoacetate. Here, we show that the same cis elements control both promoter inducibility and AtoC binding. Chromatin immunoprecipitation experiments confirmed the acetoacetate-inducible binding of AtoC to the predicted DNA region in vivo. DNase I protection footprinting analysis revealed that AtoC binds two 20-bp stretches, constituting an inverted palindrome, that are located at –146 to –107 relative to the transcription initiation site. Analyses of promoter mutants obtained by in vitro chemical mutagenesis of the atoDAEB promoter verified both the importance of AtoC binding for the inducibility of the promoter by acetoacetate and the ⁵⁴ dependence of atoDAEB expression. The integration host factor was also identified as a critical component of the AtoC-mediated induction of atoDAEB.

Published ahead of print on 6 July 2007.

Present address: Laboratory of Prokaryotic Molecular Genetics, Smurfit Institute of Genetics, Trinity College, Dublin, Ireland.