title: The production of IL-10 by human regulatory T cells is enhanced by IL-2 through a STAT5-responsive intronic enhancer in the IL-10 locus.
abstract: STAT5 molecules are key components of the IL-2 signaling pathway, the deficiency of which often results in autoimmune pathology due to a reduced number of CD4(+)CD25(+) naturally occurring regulatory T (Treg) cells. One of the consequences of the IL-2-STAT5 signaling axis is up-regulation of FOXP3, a master control gene for naturally occurring Treg cells. However, the roles of STAT5 in other Treg subsets have not yet been elucidated. We recently demonstrated that IL-2 enhanced IL-10 production through STAT5 activation. This occurred in two types of human Treg cells: a novel type of umbilical cord blood-derived Treg cell, termed HOZOT, and Tr1-like Treg cells, IL-10-Treg. In this study, we examined the regulatory mechanisms of IL-10 production in these Treg cells, focusing specifically on the roles of STAT5. By performing bioinformatic analysis on the IL-10 locus, we identified one STAT-responsive element within intron 4, designated I-SRE-4, as an interspecies-conserved sequence. We found that I-SRE-4 acted as an enhancer element, and clustered CpGs around the I-SRE-4 were hypomethylated in IL-10-producing Treg cells, but not in other T cells. A gel-shift analysis using a nuclear extract from IL-2-stimulated HOZOT confirmed that CpG DNA methylation around I-SRE-4 reduced STAT5 binding to the element. Chromatin immunoprecipitation analysis revealed the in situ binding of IL-2-activated STAT5 to I-SRE-4. Thus, we provide molecular evidence for the involvement of an IL-2-STAT5 signaling axis in the expression of IL-10 by human Treg cells, an axis that is regulated by the intronic enhancer, I-SRE-4, and epigenetic modification of this element.
authors.affiliation: Cell Biology Institute, Research Center, Hayashibara Biochemical Laboratories, Fujisaki, Okayama, Japan.
authors.forename: Kazue
authors.initials: K
authors.lastname: Tsuji-Takayama
authors.forename: Motoyuki
authors.initials: M
authors.lastname: Suzuki
authors.forename: Mayuko
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Akira
authors.initials: A
authors.lastname: Harashima
authors.forename: Ayumi
authors.initials: A
authors.lastname: Okochi
authors.forename: Takeshi
authors.initials: T
authors.lastname: Otani
authors.forename: Toshiya
authors.initials: T
authors.lastname: Inoue
authors.forename: Akira
authors.initials: A
authors.lastname: Sugimoto
authors.forename: Terumasa
authors.initials: T
authors.lastname: Toraya
authors.forename: Makoto
authors.initials: M
authors.lastname: Takeuchi
authors.forename: Fumiyuki
authors.initials: F
authors.lastname: Yamasaki
authors.forename: Shuji
authors.initials: S
authors.lastname: Nakamura
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Kibata