Two nuclear factor binding domains activate expression from the human amyloid beta-protein precursor promoter.

Abstract

Amyloid beta-protein is derived from the amyloid beta-protein precursor (APP), and it is a major component of brain amyloid depositions in Alzheimer's disease and Down's syndrome. Overexpression of APP may be one of several factors contributing to amyloid formation. The APP promoter was therefore analyzed to determine the mechanism by which APP gene expression is regulated. Cell type-specific expression from the human APP promoter is accomplished with 94 base pairs upstream from the main transcriptional start site. This promoter region contains two nuclear factor binding domains, designated APB alpha and APB beta. The contribution of these binding domains to promoter activity was analyzed by transient transfection in HeLa and PC-12 cells. Under standard culture conditions, at least 70-90% of the total activity from the APP promoter can be attributed to binding domain APB beta. The recognition domain for this nuclear factor binding site is defined by the sequence GCCGCTAGGGGT (position -93 to -82). The contribution of binding site APB alpha to APP promoter activity is considerably lower and represents 10-30% of the total activity. The recognition site for the nuclear factor that binds to APB alpha is delineated by the sequence GGATCAGCTGAC (position -53 to -42). Elimination of both binding sites causes APP promoter activity in vivo to decline to near background levels.