An updated view on transcription factor GATA3-mediated regulation of Th1 and Th2 cell differentiation

Ryoji Yagi 0 Jinfang Zhu 0 William E. Paul 0 0 Laboratory of Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health , Bethesda, MD 20892 , USA CD4 Th are critical for orchestrating adaptive immune responses. The expression of the transcription factor GATA3 (GATA-binding protein 3) is up-regulated or down-regulated during Th2 or Th1 cell differentiation, respectively. Furthermore, GATA3 is responsible for induction of Th2 differentiation and represses Th1 differentiation. In this review, we present an updated view on the molecular mechanisms through which GATA3 regulates Th1/Th2 differentiation. During Th2 cell differentiation, GATA3 directly binds to the Th2 cytokine gene locus at several regions and regulates expression. On the other hand, GATA3 inhibits Th1 cell differentiation by preventing up-regulation of IL-12 receptor b2 and STAT4 (signal transducer and activator of transcription 4) and neutralization of Runx3 (runtrelated transcription factor 3) function through protein-protein interaction. GATA3 may also directly act on the Ifng gene. In summary, GATA3 serves as a transcriptional activator or repressor through direct action on transcriptional machinery and/or affecting chromatin remodeling at many critical loci encoding cytokines, cytokine receptors, signaling molecules as well as transcription factors that are involved in the regulation of Th1 and Th2 differentiation. Introduction Naive CD4 T cells have the potential to differentiate into several alternative cell types of which the most intensively studied are Th1 and Th2 cells (1). When innate immune cells recognize invasion of intracellular pathogens such as protozoa, bacteria or viruses, naive CD4 T cells differentiate into Th1 cells, which secrete IFN-c, IL-2 and tumor necrosis factor-b. Th1 cells activate macrophages and CD8 T cells leading, under the right set of circumstances, to pathogen eradication. On the other hand, when innate immune cells recognize extracellular parasites such as helminths, the naive CD4 T cells differentiate into Th2 cells, which secrete IL-4, IL-5 and IL-13. Th2 cells activate B cells to induce immunoglobulin class switching and epithelial cells to enhance their mucus production; Th2 cells also recruit mast cells and eosinophils to infection sites to aid in the clearance of parasites. Inappropriate activation of Th1 or Th2 cells to self-antigens or to harmless foreign antigens may cause autoimmune or allergic diseases. Thus, understanding the molecular mechanisms underlying the differentiation of naive CD4 T cells into Th1 or Th2 cells is of considerable importance. Th1/Th2 differentiation is regulated by the cytokine milieu at the time of TCR engagement. This milieu is created under the influence of the particular pathogens as well as the dose of antigens and the genetic background of the host (2, 3). When naive CD4 T cells are activated through their TCR together with IL-12- or IL-4-mediated signaling, these cells differentiate into Th1 or Th2 cells, respectively. IL-12-stimulated CD4 T cells up-regulate the expression of the transcription factor T-bet (T-box expressed in T cells) and acquire their capability to produce IFN-c; activated CD4 T cells that receive IL-4 signaling up-regulate GATA3 (GATA-binding protein 3) and become capable of producing Th2 cytokines. Indeed, cytokine-mediated up-regulation of these lineagespecific transcription factors determines CD4 T-cell fate. Not only is GATA3 indispensable for Th2 differentiation and Th2 cytokine production, it is also essential for inhibition of Th1 differentiation and IFN-c production. Here, we discuss the role of GATA3 in regulating Th1 and Th2 differentiation and the molecular mechanisms involved. Functions of GATA3 in regulating Th2 cell differentiation GATA3 expression is necessary for the development of CD4 single-positive (SP) cells in the thymus (4, 5). It continues to be expressed in naive CD4 T cells at a basal level. When naive CD4 T cells are activated under Th1- or Th2-skewing conditions, GATA3 is either down-regulated or up-regulated. GATA3 up-regulation is induced by IL-4STAT6-mediated signaling (6, 7). A low dose but not high dose of antigen stimulation through TCR results in IL-4-independent GATA3 up-regulation and IL-4 production (8). Enforced expression of GATA3 has also been reported to up-regulate endogenous GATA3 expression (9). GATA3 is regarded as the master regulator to induce Th2 differentiation (10, 11) since enforced GATA3 expression induces Th2 differentiation even when the cells are cultured under Th1-skewing conditions (12) and GATA3-deficient Th2 cells fail to produce IL-4, IL-5 and IL-13 (13, 14). It has been reported that histone modifications, such as histone H3 lysine 4 (H3K4) methylation and H3K14 acetylation, are induced at the Th2 cytokine gene locus (which includes the genes for IL-4, IL-13 and IL-5) during Th2 differentiation (15). These histone modifications change the chromatin structure so that the modified regions become accessible to transcription factors and are associated with DNase I hypersensitive (HS) sites. Chromatin remodeling at the Th2 cytokine gene locus is necessary for efficient expression of IL-4, IL-5 and IL-13 in Th2 cells and it has been proposed that GATA3 regulates chromatin remodeling. GATA3 has been reported to bind to several regulatory elements at the Th2 cytokine gene locus (Fig. 1) including conserved non-coding sequence (CNS)-1, HSVa, the conserved GATA response element (CGRE), the Il5 promoter and HSII in intron 2 of the Il4 gene (1620). CNS-1, which includes two HS sites, HSS1 and HSS2, is located at the intergenic region of the Il4 and Il13 genes (21). A mobility shift assay showed that GATA3 binds to HSS2 (16, 17). In mice from which the 0.5-kbp genomic DNA segment containing the CNS-1 region was deleted, isolated CD4 T cells that were cultured under Th2-skewing conditions had diminished numbers of IL-4-producing cells and the mean fluorescence intensity of the IL-4 producers was lower (22). These mutant mice also produced less IL-4 in vivo (22). Interestingly, bone marrow-derived mast cells from these CNS-1 / mice produced normal levels of IL-4, consistent with the observation that in mast cells, HS sites were not found in CNS-1 (23). Although the CNS-1 region H3K4me1,me2,me3 appears to be critical for IL-4 production in Th2 cells, our genome-wide GATA3 ChIPseq (chromatin immunoprecipitation followed by high-throughput sequencing) data did not reveal significant GATA3 binding to CNS-1 (24), suggesting that this region recruits other critical transcription factors that promote IL-4 production in Th2 cells. HSVa is located 5-kbp downstream of the 3# end of the Il4 coding region; its DNase I HS is induced in Th2 cells upon re-stimulation (18). Both GATA3 and NFAT1 (nuclear factor of activated T cells 1) bind to HSVa in Th2 but not Th1 clones (18). Th2 cells generated from mice in which a 3.7-kbp r (...truncated)