Interferon-γ suppresses activin A/NF-E2 induction of erythroid gene expression through the NF-κB/c-Jun pathway

Interferon (IFN)-gamma is a proinflammatory cytokine that is linked to erythropoiesis inhibition and may contribute to anemia. However, the mechanism of IFN-gamma-inhibited erythropoiesis is unknown. Activin A, a member of the transforming growth factor (TGF)-beta superfamily, induces the erythropoiesis of hematopoietic progenitor cells. In this study, a luciferase reporter assay showed that IFN-gamma suppressed activin A-induced zeta-globin promoter activation in K562 erythroblast cells in a dose-dependent manner. Activin A reversed the suppressive effect of IFN-gamma on the luciferase activity of zeta-globin promoter in a dose-dependent manner. IFN-gamma also suppressed the activation of activin A-induced alpha-globin promoter. IFN-gamma reduced the mRNA expression of alpha-globin, zeta-globin, NF-E2p45, and GATA-1 induced by activin A. The results also showed that IFN-gamma induced c-Jun expression when NF-kappa Bp65 and c-Jun bound to two AP-1-binding sites on the c-Jun promoter. The luciferase activity of alpha-globin and zeta-globin promoters were enhanced by wild-type c-Jun and eliminated by dominant-negative (DN) c-Jun. The suppressive effects of IFN-gamma on the mRNA expression of alpha-globin and zeta-globin were absent in cells expressing DN c-Jun. The ability of NF-E2 to enhance activin A-induced zeta-globin promoter activation decreased when c-Jun was present, and IFN-gamma treatment further enhanced the decreasing effect of c-Jun. Chromatin immunoprecipitation revealed that NF-E2p45 bound to the upstream regulatory element (HS-40) of the alpha-globin gene cluster in response to activin A, whereas c-Jun eliminated this binding. These results suggest that IFN-gamma modulates NF-kappa B/c-Jun to antagonize activin A-mediated NF-E2 transcriptional activity on globin gene expression.