The 5'HS2 of the globin locus control region enhances transcription through the interaction of a multimeric complex binding at two functionally distinct NF-E2 binding sites

Abstract

The locus control region (LCR) of the human beta-globin locus consists of four hypersensitive regions (5'HS 1-4). One of these sites, 5'HS2, is active in both transient and stable transfection assays and transgenic mice. It has previously been shown that the jun/fos consensus binding sites in 5'HS2 are required for high levels of transcription. In this paper we show that it is the 5' of the two consensus sites that is required for this function with a contribution of the 3' site to the overall activity. The functional complex at both sites includes NF-E2. Its role in HS2 is to provide 'enhancer' activity but is not required for position independent activation. High levels of enhancement are achieved by interaction of the NF-E2 sites with three downstream elements. One of these sites binds the known factor GATA-1, whereas the other two interact with two novel DNA binding factors (H-BP and J-BP).