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HilD induces expression of Salmonella pathogenicity island 2 genes by displacing the global negative regulator H-NS from ssrAB.
J Bacteriol. 2014 Nov; 196(21):3746-55.JB

Abstract

Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2) have essential roles in the pathogenesis of Salmonella enterica. Previously, we reported transcriptional cross talk between SPI-1 and SPI-2 when the SPI-1 regulator HilD induces expression of the SsrA/B two-component system, the central positive regulator of SPI-2, during the growth of Salmonella to late stationary phase in LB rich medium. Here, we further define the mechanism of the HilD-mediated expression of ssrAB. Expression analysis of cat transcriptional fusions containing different regions of ssrAB revealed the presence of negative regulatory sequences located downstream of the ssrAB promoter. In the absence of these negative cis elements, ssrAB was expressed in a HilD-independent manner and was no longer repressed by the global regulator H-NS. Consistently, when the activity of H-NS was inactivated, the expression of ssrAB also became independent of HilD. Furthermore, electrophoretic mobility shift assays showed that both HilD and H-NS bind to the ssrAB region containing the repressing sequences. Moreover, HilD was able to displace H-NS bound to this region, whereas H-NS did not displace HilD. Our results support a model indicating that HilD displaces H-NS from a region downstream of the promoter of ssrAB by binding to sites overlapping or close to those sites bound by H-NS, which leads to the expression of ssrAB. Although the role of HilD as an antagonist of H-NS has been reported before for other genes, this is the first study showing that HilD is able to effectively displace H-NS from the promoter of one of its target genes.

Authors+Show Affiliations

Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico.Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, Mexico victor@ibt.unam.mx.

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

25135218

Citation

Martínez, Luary C., et al. "HilD Induces Expression of Salmonella Pathogenicity Island 2 Genes By Displacing the Global Negative Regulator H-NS From SsrAB." Journal of Bacteriology, vol. 196, no. 21, 2014, pp. 3746-55.
Martínez LC, Banda MM, Fernández-Mora M, et al. HilD induces expression of Salmonella pathogenicity island 2 genes by displacing the global negative regulator H-NS from ssrAB. J Bacteriol. 2014;196(21):3746-55.
Martínez, L. C., Banda, M. M., Fernández-Mora, M., Santana, F. J., & Bustamante, V. H. (2014). HilD induces expression of Salmonella pathogenicity island 2 genes by displacing the global negative regulator H-NS from ssrAB. Journal of Bacteriology, 196(21), 3746-55. https://doi.org/10.1128/JB.01799-14
Martínez LC, et al. HilD Induces Expression of Salmonella Pathogenicity Island 2 Genes By Displacing the Global Negative Regulator H-NS From SsrAB. J Bacteriol. 2014;196(21):3746-55. PubMed PMID: 25135218.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - HilD induces expression of Salmonella pathogenicity island 2 genes by displacing the global negative regulator H-NS from ssrAB. AU - Martínez,Luary C, AU - Banda,María M, AU - Fernández-Mora,Marcos, AU - Santana,Francisco J, AU - Bustamante,Víctor H, Y1 - 2014/08/18/ PY - 2014/8/20/entrez PY - 2014/8/20/pubmed PY - 2014/12/15/medline SP - 3746 EP - 55 JF - Journal of bacteriology JO - J Bacteriol VL - 196 IS - 21 N2 - Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2) have essential roles in the pathogenesis of Salmonella enterica. Previously, we reported transcriptional cross talk between SPI-1 and SPI-2 when the SPI-1 regulator HilD induces expression of the SsrA/B two-component system, the central positive regulator of SPI-2, during the growth of Salmonella to late stationary phase in LB rich medium. Here, we further define the mechanism of the HilD-mediated expression of ssrAB. Expression analysis of cat transcriptional fusions containing different regions of ssrAB revealed the presence of negative regulatory sequences located downstream of the ssrAB promoter. In the absence of these negative cis elements, ssrAB was expressed in a HilD-independent manner and was no longer repressed by the global regulator H-NS. Consistently, when the activity of H-NS was inactivated, the expression of ssrAB also became independent of HilD. Furthermore, electrophoretic mobility shift assays showed that both HilD and H-NS bind to the ssrAB region containing the repressing sequences. Moreover, HilD was able to displace H-NS bound to this region, whereas H-NS did not displace HilD. Our results support a model indicating that HilD displaces H-NS from a region downstream of the promoter of ssrAB by binding to sites overlapping or close to those sites bound by H-NS, which leads to the expression of ssrAB. Although the role of HilD as an antagonist of H-NS has been reported before for other genes, this is the first study showing that HilD is able to effectively displace H-NS from the promoter of one of its target genes. SN - 1098-5530 UR - https://www.unboundmedicine.com/medline/citation/25135218/HilD_induces_expression_of_Salmonella_pathogenicity_island_2_genes_by_displacing_the_global_negative_regulator_H_NS_from_ssrAB_ L2 - https://journals.asm.org/doi/10.1128/JB.01799-14?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -