The identification of hematopoietic-specific regulatory elements for WASp gene expression

Chromosome Conformation Capture (3C) technology was used to identify physical interactions between the proximal Wiskott-Aldrich Syndrome protein (WASp) promoter and its distant DNA segments in Jurkat-T cells. We found that two hematopoietic specific DNase I hypersensitive (DHS) sites (proximal DHS-A, and distal DHS-B) which had high interaction frequencies with the proximal WASp promoter indicating potential regulatory activity for these DHS sites. Subsequently, we cloned several DNA fragments around the proximal DHS-A site into a luciferase reporter vector. Interestingly, no fragments showed enhancer activity, but two fragments exhibited strong silencing activity in Jurkat-T cells. After aligning the chromatin state profiling for hematopoietic and nonhematopoietic cells using the human genome browser (UCSC), we found a 5 kb putative hematopoietic specific enhancer region located 250 kb downstream of the WAS gene. This putative enhancer region contains two hematopoietic cell specific DHS sites. Subsequently, the hematopoietic specific DHS sites enhanced luciferase expression from the proximal WASp promoter in all hematopoietic cells we tested. Finally, using a lentiviral vector stable expression system, the hematopoietic specific-enhancer(s) increased GFP reporter gene expression in hematopoietic cells, and increased WASp gene expression in WASp deficient cells. This enhancer may have the potential to be used in gene therapy for hematological diseases.