Tags

Type your tag names separated by a space and hit enter

HilE Regulates HilD by Blocking DNA Binding in Salmonella enterica Serovar Typhimurium.
J Bacteriol. 2018 04 15; 200(8)JB

Abstract

The Salmonella type three secretion system (T3SS), encoded in the Salmonella pathogenicity island 1 (SPI1) locus, mediates the invasion of the host intestinal epithelium. SPI1 expression is dependent upon three AraC-like regulators: HilD, HilC, and RtsA. These regulators act in a complex feed-forward loop to activate each other and hilA, which encodes the activator of the T3SS structural genes. HilD has been shown to be the major integration point of most signals known to activate the expression of the SPI1 T3SS, acting as a switch to control induction of the system. HilE is a negative regulator that acts upon HilD. Here we provide genetic and biochemical data showing that HilE specifically binds to HilD but not to HilC or RtsA. This protein-protein interaction blocks the ability of HilD to bind DNA as shown by both an in vivo reporter system and an in vitro gel shift assay. HilE does not affect HilD dimerization, nor does it control the stability of the HilD protein. We also investigated the role of HilE during the infection of mice using competition assays. Although deletion of hilE does not confer a phenotype, the hilE mutation does suppress the invasion defect conferred by loss of FliZ, which acts as a positive signal controlling HilD protein activity. Together, these data suggest that HilE functions to restrict low-level HilD activity, preventing premature activation of SPI1 until positive inputs reach a threshold required to fully induce the system.IMPORTANCESalmonella is a leading cause of gastrointestinal and systemic disease throughout the world. The SPI1 T3SS is required for Salmonella to induce inflammatory diarrhea and to gain access to underlying tissue. A complex regulatory network controls expression of SPI1 in response to numerous physiological inputs. Most of these signals impinge primarily on HilD translation or activity. The system is triggered when HilD activity crosses a threshold that allows efficient activation of its own promoter. This threshold is set by HilE, which binds to HilD to prevent the inevitable minor fluctuations in HilD activity from inappropriately activating the system. The circuit also serves as a paradigm for systems that must integrate numerous environmental parameters to control regulatory output.

Authors+Show Affiliations

Department of Microbiology, University of Illinois, Urbana, Illinois, USA.Department of Microbiology, University of Illinois, Urbana, Illinois, USA.Department of Microbiology, University of Illinois, Urbana, Illinois, USA.Department of Microbiology, University of Illinois, Urbana, Illinois, USA slauch@illinois.edu.

Pub Type(s)

Journal Article
Research Support, N.I.H., Extramural

Language

eng

PubMed ID

29378886

Citation

Grenz, Jesse R., et al. "HilE Regulates HilD By Blocking DNA Binding in Salmonella Enterica Serovar Typhimurium." Journal of Bacteriology, vol. 200, no. 8, 2018.
Grenz JR, Cott Chubiz JE, Thaprawat P, et al. HilE Regulates HilD by Blocking DNA Binding in Salmonella enterica Serovar Typhimurium. J Bacteriol. 2018;200(8).
Grenz, J. R., Cott Chubiz, J. E., Thaprawat, P., & Slauch, J. M. (2018). HilE Regulates HilD by Blocking DNA Binding in Salmonella enterica Serovar Typhimurium. Journal of Bacteriology, 200(8). https://doi.org/10.1128/JB.00750-17
Grenz JR, et al. HilE Regulates HilD By Blocking DNA Binding in Salmonella Enterica Serovar Typhimurium. J Bacteriol. 2018 04 15;200(8) PubMed PMID: 29378886.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - HilE Regulates HilD by Blocking DNA Binding in Salmonella enterica Serovar Typhimurium. AU - Grenz,Jesse R, AU - Cott Chubiz,Jessica E, AU - Thaprawat,Pariyamon, AU - Slauch,James M, Y1 - 2018/03/26/ PY - 2017/12/12/received PY - 2018/01/18/accepted PY - 2018/1/31/pubmed PY - 2019/3/21/medline PY - 2018/1/31/entrez KW - HilD KW - HilE KW - SPI1 KW - Salmonella JF - Journal of bacteriology JO - J Bacteriol VL - 200 IS - 8 N2 - The Salmonella type three secretion system (T3SS), encoded in the Salmonella pathogenicity island 1 (SPI1) locus, mediates the invasion of the host intestinal epithelium. SPI1 expression is dependent upon three AraC-like regulators: HilD, HilC, and RtsA. These regulators act in a complex feed-forward loop to activate each other and hilA, which encodes the activator of the T3SS structural genes. HilD has been shown to be the major integration point of most signals known to activate the expression of the SPI1 T3SS, acting as a switch to control induction of the system. HilE is a negative regulator that acts upon HilD. Here we provide genetic and biochemical data showing that HilE specifically binds to HilD but not to HilC or RtsA. This protein-protein interaction blocks the ability of HilD to bind DNA as shown by both an in vivo reporter system and an in vitro gel shift assay. HilE does not affect HilD dimerization, nor does it control the stability of the HilD protein. We also investigated the role of HilE during the infection of mice using competition assays. Although deletion of hilE does not confer a phenotype, the hilE mutation does suppress the invasion defect conferred by loss of FliZ, which acts as a positive signal controlling HilD protein activity. Together, these data suggest that HilE functions to restrict low-level HilD activity, preventing premature activation of SPI1 until positive inputs reach a threshold required to fully induce the system.IMPORTANCESalmonella is a leading cause of gastrointestinal and systemic disease throughout the world. The SPI1 T3SS is required for Salmonella to induce inflammatory diarrhea and to gain access to underlying tissue. A complex regulatory network controls expression of SPI1 in response to numerous physiological inputs. Most of these signals impinge primarily on HilD translation or activity. The system is triggered when HilD activity crosses a threshold that allows efficient activation of its own promoter. This threshold is set by HilE, which binds to HilD to prevent the inevitable minor fluctuations in HilD activity from inappropriately activating the system. The circuit also serves as a paradigm for systems that must integrate numerous environmental parameters to control regulatory output. SN - 1098-5530 UR - https://www.unboundmedicine.com/medline/citation/29378886/HilE_Regulates_HilD_by_Blocking_DNA_Binding_in_Salmonella_enterica_Serovar_Typhimurium_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=29378886 DB - PRIME DP - Unbound Medicine ER -