Developmentally specific role of the CCAAT box in regulation of human gamma-globin gene expression.

The CCAAT box is a widespread motif in eukaryotic promoters. In this study we demonstrate that the effects of the CCAAT box on gamma-globin gene activation are developmentally distinct. Although this promoter element is essential for high level gamma gene expression in adult erythropoiesis, it plays little role in embryonic erythroid cells. The CCAAT mutation in the human gamma-globin gene promoter impairs recruitment of TATA-binding protein (TBP), TFIIB, and RNA polymerase II in adult splenic erythroblasts but not in embryonic erythroid cells. We also show that the efficiency of gamma gene transcription is correlated with recruitment of TBP on the TATA box but that the level of TBP recruitment is not nuclear factor Y (NF-Y)-dependent. Our data also suggest that it is unlikely that transcriptional stimulation by the CCAAT box is exerted through direct protein-protein interaction between NF-Y and TBP.