In an initial series of studies we generated a series of reporter constructs containing regions of the IL-17 gene upstream of this transcription start site and then assessed the activity of these constructs following their transfection into Jurkat cells and stimulation with PMA and ionomycin. We found that whereas the lineage-specific IL-17 transcription factor, RORgamma-t. is present in a 1.1kb promoter fragment and this factor is necessary for IL-17 transcription, optimal IL-17 transcription requires the presence of a 2kb promoter fragment containing up-stream sequence that does not bind RORgamma-t. In further studies we identified Runx (particularly Runx1) as another IL-17 transcription factor that binds to the IL-17 promoter at an up-stream site. However, whereas this transcription factor was critically necessary for optimal IL-17 transcription it is totally dependent on RORgamma-t binding and activity. In yet other studies we identified at least one distal (up-stream) conserved non-coding sequence (CNS sequence) that contains binding sites for both RORgamma-t and Runx and which is necessary for IL-17 transcription.? ? To substantiate the above findings in CD4+ T cells undergoing Th17 differentiation we conducted extensive studies in which we evaluated the effect of Runx1 (or Runx2) down-regulation of IL-17 expression. These studies involved the transfection of cells with Runx-specific siRNA or the transduction of cells with a retrovirus expressing either a short-hairpin siRNA or a dominant-negative Runx construct. The results of these studies were congruent in that they showed that down-regulation of Runx led to greatly decrease IL-17 production. However, as presaged by the reporter studies discussed above, down-regulation of Runx1 in cells cultured under conditions leading to the absence of RORgammat or only small amounts of RORgammat, had no or little effect on IL-17 expression. In related studies we showed using ChIP assays that both RORgamma-t and Runx1 bind to the IL-17 promoter and the CNS enhancer of T cells undergoing Th17 differentiation.? ? Recently it has been shown that Foxp3, the lineage-specific factor of regulatory T cells interacts with RORgamma-t and thereby down-regulates the latters capacity to induce IL-17 expression. To explore the regulatory activity of Foxp3 in relation to the role of Runx in IL-17 transcription we performed co-transfection studies of CD4+ T cells of Runx and Foxp3 mutants. We found that whereas wild type Foxp3 suppressed RORgamma-t-induced IL-17 expression, a Foxp3 mutant lacking the ability to bind to Runx1 had no effect. These data revealed the critical fact that Foxp3 inhibition of Th17 depends both on its ability to bind to Runx and to RORgamma-t. In a final series of studies related to such binding we performed co-immunoprecipitation studies in which we showed first that Runx1 physically interacts with RORgammat and second that Foxp3 intereacts with RORgt. These data, coupled with previous data that Foxp3 physically interacts with Runx1 lead to the conclusion that a complex, three-way interaction between Runx1, Foxp3 and RORgamma-t determines the differentiation of CD4 cells into Th17 cells, or alternatively into regulatory T cells. In addition, they strongly imply that regulation of Runx1 is another way that IL-17 transcription is regulated.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Intramural Research (Z01)
Project #
1Z01AI000872-09
Application #
7732554
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
9
Fiscal Year
2008
Total Cost
$912,859
Indirect Cost
City
State
Country
United States
Zip Code
Strober, Warren; Zhang, Fuping; Kitani, Atsushi et al. (2010) Proinflammatory cytokines underlying the inflammation of Crohn's disease. Curr Opin Gastroenterol 26:310-7
Xu, Lili; Kitani, Atsushi; Fuss, Ivan et al. (2007) Cutting edge: regulatory T cells induce CD4+CD25-Foxp3- T cells or are self-induced to become Th17 cells in the absence of exogenous TGF-beta. J Immunol 178:6725-9
Strober, Warren; Fuss, Ivan; Mannon, Peter (2007) The fundamental basis of inflammatory bowel disease. J Clin Invest 117:514-21
Strober, Warren (2006) Immunology. Unraveling gut inflammation. Science 313:1052-4
Boirivant, Monica; Pallone, Francesco; Di Giacinto, Claudia et al. (2006) Inhibition of Smad7 with a specific antisense oligonucleotide facilitates TGF-beta1-mediated suppression of colitis. Gastroenterology 131:1786-98
Di Giacinto, Claudia; Marinaro, Mariarosaria; Sanchez, Massimo et al. (2005) Probiotics ameliorate recurrent Th1-mediated murine colitis by inducing IL-10 and IL-10-dependent TGF-beta-bearing regulatory cells. J Immunol 174:3237-46
Strober, Warren (2005) Downstream effector functions of T-cell activation. J Pediatr Gastroenterol Nutr 40 Suppl 1:S26
Boirivant, Monica; Strober, Warren; Fuss, Ivan J (2005) Regulatory cells induced by feeding TNP-haptenated colonic protein cross-protect mice from colitis induced by an unrelated hapten. Inflamm Bowel Dis 11:48-55
Strober, Warren; Fuss, Ivan; Boirivant, Monica et al. (2004) Insights into the mechanism of oral tolerance derived from the study of models of mucosal inflammation. Ann N Y Acad Sci 1029:115-31
Usui, Takashi; Nishikomori, Ryuta; Kitani, Atsushi et al. (2003) GATA-3 suppresses Th1 development by downregulation of Stat4 and not through effects on IL-12Rbeta2 chain or T-bet. Immunity 18:415-28

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