Protein-DNA interactions in the promoter region of the amyloid precursor protein (APP) gene in human neocortex

Abstract

We have investigated protein-DNA interactions in the proximal promotor of the human amyloid precursor protein (APP) gene in temporal lobe neocortical nuclei isolated from control and Alzheimer disease (AD) affected brains. We report that the human APP 5′ promotor sequence from −203 to +55 bp, which has been previously reported to contain essential regulatory elements for APP gene transcription, lies in a deoxyribonuclease I, micrococcal nuclease- and restriction endonuclease-sensitive, G+C-rich nucleosome-free gap flanked both 5′ and 3′ by typical nucleosome structures. As analyzed by electrophoretic mobility shift assay, this extended internucleosomal linker DNA is heavily occupied by nuclear protein factors, and interacts differentially with nuclear protein extracts obtained from HeLa and human brain neocortical nuclei. This suggests that the chromatin conformation of the APP gene promoter may vary in different cell types, and may correlate with differences in APP gene expression. Human recombinant transcription factors AP1, SP1 and TFIID (but not AP2 or brain histones H1, H2B and H4) interact with the −203 to +55 bp of the human APP promotor sequence. Only minor differences were observed in the chromatin structure of the immediate APP promotor between non-AD and AD affected neocortical nuclei, suggesting either that post-transcriptional processes, or that regulatory elements lying elsewhere in the APP gene may be important in the aberrant accumulation of the APP gene product.