Figure 4. AhR and c-Maf transactivate the Il10 and Il21 promoters in T_R1 cells.

a) AhR and c-Maf binding sites in the Il10 and the Il21 promoters. Schematic representation of the Il10 and the Il21 promoters, AhR binding sites (XRE) are depicted as open boxes and c-Maf binding sites (MARE) are depicted as filled boxes. b) ChIP analysis of the interaction of AhR or isotype control antibody (IgG) to the XRE in the Il10 and c) the Il21 promoter in in vitro differentiated T_R1 or control T_H0 cells. (*p<0.01; **p<0.001 between AhR vs IgG) d) ChIP analysis of the interaction of c-Maf or isotype control antibody (IgG) to the MARE in the Il10 and e) the Il21 promoter in in vitro differentiated T_R1 or control T_H0 cells. (**p<0.001 between c-Maf vs IgG) f) and g) Transactivation of the Il10 or Il21 promoters by c-Maf or AhR. Reporter constructs for the Il10 f) or Il21 g) promoters (Il10-Luc and Il21-Luc, respectively) were co-transfected in EL-4 T cells with vectors coding for AhR and/or c-Maf, and firefly luciferase activity was determined 24 hours later and normalized to the renilla luciferase activity of a co-transfected control. (**p<0.001) h) In vitro differentiated T_H0 or T_R1 cell expression of AhR and c-Maf (immunoblot; IB, left panel). AhR was immunoprecipitated from nuclear extracts with a specific antibody (IP, right panel), c-Maf and AhR complexes immunoblotted (right panel) using an anti-c-Maf antibody.