Abstract
The Hha family of proteins is involved in the regulation of gene expression in enterobacteria by forming complexes with H-NS-like proteins. Whereas several amino acid residues of both proteins participate in the interaction, some of them play a key role. Residue D48 of Hha protein is essential for the interaction with H-NS, thus the D48N substitution in Hha protein abrogates H-NS/Hha interaction. Despite being a paralog of H-NS protein, StpA interacts with HhaD48N with higher affinity than with the wild type Hha protein. To analyze whether Hha is capable of acting independently of H-NS and StpA, we conducted transcriptomic analysis on the hha and stpA deletion strains and the hhaD48N substitution strain of Salmonella Typhimurium using a custom microarray. The results obtained allowed the identification of 120 genes regulated by Hha in an H-NS/StpA-independent manner, 38% of which are horizontally acquired genes. A significant number of the identified genes are involved in functions related to cell motility, iron uptake, and pathogenicity. Thus, motility assays, siderophore detection and intra-macrophage replication assays were performed to confirm the transcriptomic data. Our findings point out the importance of Hha protein as an independent regulator in S. Typhimurium, highlighting a regulatory role on virulence.
Highlights
One of the relevant features of bacterial cells is their ability to sense and adapt to a usually rapidly changing environment
In this work we identify the set of genes of Salmonella enterica serovar Typhimurium SV5015 that are under the regulation of the Hha protein in an H-NS/StpA-independent manner
Hha residues involved in StpA interaction are the same as for the H-NS protein
Summary
One of the relevant features of bacterial cells is their ability to sense and adapt to a usually rapidly changing environment. Bacteria have developed several mechanisms to detect and transduce external stimuli resulting in modifications of the gene expression pattern. Nucleoid-associated proteins play relevant roles in bacteria, both organizing the chromosome and influencing gene expression. A well-known example is the nucleoid-associated protein H-NS. The H-NS protein is widely distributed within Gram-negative bacteria and is one of the best characterized examples of a modulator that influences gene expression in response to environmental stimuli (Dorman, 2007). In Escherichia coli, up to 5% of the genes are subjected to H-NS regulation (Hommais et al, 2001). In Salmonella Typhimurium, approximately 9% of the genes show an H-NS-dependent regulation (Lucchini et al, 2006; Navarre et al, 2006).
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