The binding of the ubiquitous transcription factor Sp1 at the locus control region represses the expression of β-like globin genes

Abstract

To investigate the function of transcription factor Sp1 in β-like globin gene activation, we analyzed the recruitment of Sp1, fetal Krüppel-like factor 2 (FKLF2), and related factors at the human β-globin locus in a human fetal liver and mouse erythroleukemia hybrid cell (A181γ cell) that contains a single copy of human chromosome 11. Sp1 binds at the GT boxes of the cis-elements throughout the β-locus, but it is phosphorylated and lost over DNase I hypersensitive site (HS)2, HS3, HS4, and the human β-globin gene promoter after A181γ cell differentiation. The binding of FKLF2 at HS2 and HS3 was unchanged. Histone deacetylase 1, which could be recruited by Sp1, is also lost over HS2 and HS3 after differentiation, resulting in the acetylation of histones 3 and 4 across the human β-globin locus. We previously detected in vivo GT footprints over the β-globin locus after A181γ differentiation. Here, we report that after differentiation, the p300/CREB-binding protein-associated factor is recruited by FKLF2 to the locus control region to acetylate histones 3 and 4 at the human β-globin gene locus. Our results suggest that Sp1 is an inhibitor of β-like globin gene transcription during erythroid terminal differentiation. Its phosphorylation and release allow the erythroid-specific FKLF2 or erythroid Krüppel-like factor to interact with other erythroid-specific transcription factors to initiate the transcription of β-like globin genes.

• β-globin gene regulation
• erythroid-specific transcription factors
• chromatin immunoprecipitation