Targeted remodeling of human beta-globin promoter chromatin structure produces increased expression and decreased silencing

The chromatin structure of the human beta-globin gene locus assumes a trans criptionally-active conformation in erythroid cells. One feature of this ch romatin reorganization is the formation of DNase 1 hypersensitive sites in the regions of active globin gene promoters. This reorganization requires t he globin locus control region and is associated with normal expression of the beta-like globin genes. To determine whether it is possible to artifici ally enhance the opening of the chromatin structure of a minimal beta-globi n promoter, we placed a 101bp, erythroid-specific DNase 1 hypersensitive si te-forming element (HSFE) immediately upstream of the beta-globin promoter and gene. This element includes binding sites for NF-E2, AP-1, GATA-1 and S p-l, Constructs were stably transfected into murine erythroleukemia cells a nd promoter chromatin structure and gene expression were analyzed. The HSFE induced an area of enhanced DNase 1 hypersensitivity extending from the tr anscriptional start site to -300bp of the artificial promoter and significa ntly increased the proportion of beta-globin promoters in an open chromatin configuration. This remodeling of promoter chromatin structure resulted in 3-fold increases in beta-globin gene transcription and induction, and inhi bited long-term beta-globin gene silencing. These results indicate that a r elatively small cis-acting element is able to enhance remodeling of promote r chromatin structure resulting in increased beta-globin gene expression. ( C) 1999 Academic Press.