Altered regulation of β-like globin genes by a redesigned erythroid transcription factor

Objective Targeted regulation of β-like globin genes was studied using designer zinc finger transcription factors containing the DNA binding domain of the red cell specific transcription factor erythroid Kruppel-like factor (EKLF) fused to repression domains. Methods Globin gene expression was analyzed after introduction of the modified transcription factors into cell lines, embryonic stem cells and transgenic mice. Results As would be predicted, when introduced transiently into cells these transcription factors were effective in repressing the adult β-globin promoter CACCC element, which is the natural target for EKLF. In murine erythroleukemia cells repression of the adult β-globin gene was accompanied by a reactivation of the endogenous embryonic βH1-globin gene. Studies in differentiated embryonic stem cells and transgenic mice confirmed the reactivation of embryonic gene expression during development. Conclusion Our studies support a competition model for β-globin gene expression and underscore the importance of EKLF in the embryonic/fetal-to-adult globin switch. They also demonstrate the feasibility of designer zinc finger transcription factors in the study of transcriptional control mechanisms at the β-globin locus and as potential gene therapy agents for sickle cell disease and related hemoglobinopathies.