The Uropathogenic Specific Protein Gene usp from Escherichia coli and Salmonella bongori is a Novel Member of the TyrR and H-NS Regulons

Abstract

The <i>Escherichia coli</i> PAI<i>usp</i> is a small pathogenicity island encoding <i>usp,</i> for the uropathogenic specific protein (Usp), a genotoxin and three associated downstream <i>imu1-3</i> genes that protect the producer against its own toxin. Bioinformatic analysis revealed the presence of the PAI<i>usp</i> also in publically available <i>Salmonella bongori</i> and <i>Salmonella enterica</i> subps. <i>salamae</i> genome sequences. PAI<i>usp</i> is in all examined sequences integrated within the <i>aroP-pdhR</i> chromosomal intergenic region. The focus of this work was identification of the <i>usp</i> promoter and regulatory elements controlling its activity. We show that, in both <i>E. coli</i> and <i>S. bongori</i>, the divergent TyrR regulated P3 promoter of the <i>aroP</i> gene, encoding an aromatic amino acid membrane transporter, drives <i>usp</i> transcription while H-NS acts antagonistically repressing expression. Our results show that the horizontally acquired PAI<i>usp</i> has integrated into the TyrR regulatory network and that environmental factors such as aromatic amino acids, temperature and urea induce <i>usp</i> expression.