A human β-spectrin gene promoter directs high level expression in erythroid but not muscle or neural cells

Abstract

β-Spectrin is an erythrocyte membrane protein that is defective in many patients with abnormalities of red blood cell shape including hereditary spherocytosis and elliptocytosis. It is expressed not only in erythroid tissues but also in muscle and brain. We wished to determine the regulatory elements that determine the tissue-specific expression of the β-spectrin gene. We mapped the 5'-end of the β-spectrin erythroid cDNA and cloned the 5'-flanking genomic DNA containing the putative β-spectrin gene promoter. Using transfection of promoter/reporter plasmids in human tissue culture cell lines, in vitro DNase I footprinting analyses, and gel mobility shift assays, a β-spectrin gene erythroid promoter with two binding sites for GATA-1 and one site for CACCC-related proteins was identified. All three binding sites were required for full promoter activity; one of the GATA-1 motifs and the CACCC-binding motif were essential for activity. The β-spectrin gene promoter was able to be transactivated in heterologous cells by forced expression of GATA-1. In transgenic mice, a reporter gene directed by the β- spectrin promoter was expressed in erythroid tissues at all stages of development. Only weak expression of the reporter gene was detected in muscle and brain tissue, suggesting that additional regulatory elements are required for high level expression of the β-spectrin gene in these tissues.