Requirement of a distal AT-motif for TGF-β-mediated repression of the activity of the AFP promoter. (a) Schematic presentation of TK.Luc conjugated with several fragments of the AFP promoter between −4990 and −2968. (b) Effect of TGF-β on the activity of TK.Luc reporters conjugated with several truncated AFP promoter regions. Each reporter (200 ng) was transfected into HepG2 cells. The cells were then stimulated with 5 ng/mL TGF-β. (c) Schematic presentation of 0.2Luc conjugated with several fragments of the AFP promoter between −3658 and −3148. (d) Effect of TGF-β on the activity of the luciferase reporters described in Figure 3(c). Each reporter (200 ng) was transfected into HepG2 cells. The cells were then stimulated with 5 ng/mL TGF-β. (e) Requirement of the fragment between −3562 and −3422 for TGF-β-mediated suppression of the AFP promoter. HepG2 cells were transfected with the indicated plasmids (200 ng). The cells were then stimulated with 5 ng/mL TGF-β. (f) Cooperation of ATBF1 with the TGF-β signaling for 3′52Luc activity. HepG2 cells were transfected with either 3.52Luc reporter (200 ng) in the presence or absence of ATBF1 (200 ng). The cells were then stimulated with 5 ng/mL TGF-β.