We isolated splenic naive CD4 T cells from C57BL/6 mice and stimulated them in vitro in either Th1 or Selleck Fluorouracil Th2 polarizing conditions. Cells were cross-linked and sonicated, and the chromatin was immunoprecipitated with either an anti-GATA-3 or anti-MTA-2 antibody. GATA-3
bound to Th2 LCR (RHS4, RHS5, RHS6, and RHS7), the promoters of il4, il5 and il13 genes, and enhancers (CNS-1 and CNS-2/HSV) in a Th2-specific manner (Fig. 2). This result shows that GATA-3 binds to the Th2 cytokine locus globally and to Th2 specifically. The MTA-2 also bound to Th2 LCR (RHS4, RHS5, RHS6, and RHS7) and promoters of Th2 cytokine genes, and enhancers (CNS-1/HSS, CNS-2/HSV) (Fig. 2). However, in contrast to GATA-3, MTA-2 bound to these regions in a Th1-specific manner (Fig. 2). Therefore, the overall binding of MTA-2 and GATA-3 on the Th2 cytokine C59 wnt concentration locus was mutually exclusive (Fig. 2). Interestingly, both GATA-3 and MTA-2 bound to the promoter of the ifng gene in Th2 cells (Fig. 2). The simultaneous binding of GATA-3 and MTA-2 on the ifng promoter was confirmed by a double-chromatin immunoprecipitation experiment. Chromatin from Th1 or Th2 cells was first immunoprecipitated with an anti-GATA-3 antibody, and the bound antibody was detached from the chromatin by treating with DTT. The eluted chromatin was then immunoprecipitated with the anti-MTA-2 antibody. The result confirms that GATA-3 and MTA-2 bound to the ifng promoter simultaneously
in Th2 cells (Fig. 3). Next, we examined whether the binding of MTA-2 to ifng promoter is dependent on GATA-3. For this purpose, we used siRNA-mediated reduction (knockdown) of GATA-3 protein in EL4 cells. We transfected gata3 siRNA into EL4 cells and measured the protein level of GATA-3 by immunoblotting (Fig. 4a).
Treatment with gata3 siRNA led to a significant reduction of GATA-3 protein level in EL4 cells (Fig. 4a). The expression of ifng gene was increased by treatment with gata3 siRNA (Fig. 4b), consistent with the previous reports.13,14 Interestingly, the binding of MTA-2 to ifng promoter was abolished by gata3 siRNA (Fig. 4c). However, the binding of MTA-2 to myc promoter, which has been shown previously24,25 but has not been Non-specific serine/threonine protein kinase shown to have any relevance to GATA-3, was not affected by gata3 siRNA (Fig. 4c). These results strongly suggest that the binding of MTA-2 to ifng promoter is specifically dependent on GATA-3. We also examined whether MTA-2 affects the functional activity of GATA-3. The GATA-3 expression vector was transfected with reporter constructs that contain IL4P-luciferase (IL4P) or RHS7-IL4P-luciferase (IL4P-RHS7).9 Introduction of GATA-3 transactivated the transcription of the reporter gene about two-fold in IL4P and about three-fold in RHS7-IL4P constructs after treatment with PMA + ionomycin (Fig. 5). These results suggest that the il4 promoter and RHS7 are GATA-3 responsible elements, and are consistent with the ChIP data indicating that GATA-3 bound to these regions (Fig. 2).