C/EBPδ and C/EBPγ bind the CCAAT-box in the human β-globin promoter and modulate the activity of the CACC-box binding protein, EKLF

Developmental- and tissue-specific expression of globin genes is mediated by a few key elements within the proximal promoter of each gene. DNA-binding assays previously identified NF-Y, GATA-1, C/EBPβ and C/EBPγ as candidate regulators of β-globin transcription via the CCAAT-box, a promoter element situated between CACC- and TATA-boxes. We have identified C/EBPδ as an additional β-globin CCAAT-box binding protein. In reporter assays, we show that C/EBPδ can co-operate with EKLF, a CACC-box binding protein, to activate the β-globin promoter, whereas C/EBPγ inhibits the transcriptional activity of EKLF in this assay.