Cloning and expression of the rat BACE1 promoter

The pathogenic processing of the amyloid precursor protein (APP) into beta-amyloid peptides, which give rise to beta-amyloid plaques in the brains of Alzheimer's disease patients, requires the enzymatic activity of the beta-site APP-cleaving enzyme 1 (BACE1). We report the cloning and sequence of a 1.5-kb DNA fragment upstream of the coding sequence of the rat BACE1 gene and the construction of a BACE1 promoter/luciferase reporter construct. The basal activity of this promoter construct was highest in neuronal cell lines such as BE(2)-C and PC12 and in the pancreatic cell line AR42J, somewhat lower in rat primary neurons, and astrocytic and microglial cultures, very low in hepatocytes, and almost absent in fibroblasts and in the monocyte-macrophage cell line RAW264.7. The first 600 bp of this promoter are highly conserved among rat, mouse, and human, suggesting that this region contains regulatory elements that modulate BACE1 transcription. Indeed, this fragment contains several putative transcription factor binding sites such as MZF1, Sp1, four GATA-1 sites, and one YY1 site. Directed mutagenesis of GATA-1 elements led to altered luciferase expression, indicating that these sites are involved in the regulation of BACE1 transcription. Additionally, the analysis of promoter activities of deletion mutants suggests the presence of activators of BACE1 transcription between bases -514 to -753 and of suppressor elements between bases -754 and -1541. The BACE1 promoter sequence data and the constructs described here will be useful to identify factors that influence the expression of BACE1 in experimental paradigms in vitro.