The distinctive roles of erythroid specific activator GATA-1 and NF-E2 in transcription of the human fetal γ-globin genes

GATA-1 and NF-E2 are erythroid specific activators that bind to the beta-globin locus. To explore the roles of these activators in transcription of the human fetal stage specific gamma-globin genes, we reduced GATA-1 and p45/NF-E2 using shRNA in erythroid K562 cells. GATA-1 or p45/NF-E2 knockdown inhibited the transcription of the gamma-globin genes, hypersensitive site (HS) formation in the LCR and chromatin loop formation of the beta-globin locus, but histone acetylation across the locus was decreased only in the case of GATA-1 knockdown. In p45/NF-E2 knockdown cells, GATA-1 binding was maintained at the LCR HSs and gamma-globin promoter, but NF-E2 binding at the LCR HSs was reduced by GATA-1 knockdown regardless of the amount of p45/NF-E2 in K562 cells. These results indicate that histone acetylation is dependent on GATA-1 binding, but the binding of GATA-1 is not sufficient for the gamma-globin transcription, HS formation and chromatin loop formation and NF-E2 is required. This idea is supported by the distinctive binding pattern of CBP and Brg1 in the beta-globin locus. Furthermore GATA-1-dependent loop formation between HS5 and 3'HS1 suggests correlation between histone modifications and chromatin looping.