TRANSFORMING-GROWTH-FACTOR-BETA STIMULATES INTERLEUKIN-11 TRANSCRIPTION VIA COMPLEX ACTIVATING PROTEIN-1-DEPENDENT PATHWAYS

Studies were undertaken to characterize the mechanism by which transfo rming growth factor-beta(1) (TGF-beta(1)) stimulates epithelial cell i nterleukin (IL)-11 production, Nuclear run-on studies demonstrated tha t TGF-beta(1) is a potent stimulator of IL-11 gene transcription. TGF- beta(1) also stimulated the luciferase activity in cells transfected w ith reporter gene constructs containing nucleotides -728 to +58 of the IL-11 promoter. Studies with progressive 5' deletion constructs and s ite-specific mutations demonstrated that this stimulation was dependen t on 2 AP-1 sites between nucleotides -100 and -82 in the IL-11 promot er. Mobility shift assays demonstrated that TGF-beta(1) stimulated AP- 1 protein-DNA binding to both AP-1 sites. Supershift analysis demonstr ated that JunD was the major moiety contributing to AP-1-DNA binding i n unstimulated cells and that c-Jun-, Fra-1-, and Fra-2-DNA binding we re increased whereas JunD-DNA binding was decreased in TGF-beta(1)-sti mulated cells. The sequence in the IL-11 promoter that contains the AP -1 sites also conferred TGF-beta(1) responsiveness, in a position-inde pendent fashion, on a heterologous minimal promoter. Thus, TGF-beta(1) stimulates IL-11 gene transcription via a complex AP-1-dependent path way that is dependent on 2 AP-1 motifs between nucleotides -100 and -8 2 that function as am enhancer in the IL-11 promoter.