PROTEIN-DNA INTERACTIONS IN THE PROMOTER REGION OF THE AMYLOID PRECURSOR PROTEIN (APP) GENE IN HUMAN NEOCORTEX

We have investigated protein-DNA interactions in the proximal promotor of the human amyloid precursor protein (APP) gene in temporal lobe ne ocortical nuclei isolated from control and Alzheimer disease (AD) affe cted brains. We report that the human APP 5' promotor sequence from -2 03 to + 55 bp, which has been previously reported to contain essential regulatory elements for APP gene transcription, lies in a deoxyribonu clease I, micrococcal nuclease- and restriction endonuclease-sensitive , G+C-rich nucleosome-free gap flanked both 5' and 3' by typical nucle osome structures. As analyzed by electrophoretic mobility shift assay, this extended internucleosomal linker DNA is heavily occupied by nucl ear 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 AP P gene expression. Human recombinant transcription factors AP1, SP1 an d TFIID (but not AP2 or brain histones H1, H2B and H4) interact with t he - 203 to + 55 bp of the human APP promotor sequence. Only minor dif ferences were observed in the chromatin structure of the immediate APP promotor between non-AD and AD affected neocortical nuclei, suggestin g either that post-transcriptional processes, or that regulatory eleme nts lying elsewhere in the APP gene may be important in the aberrant a ccumulation of the APP gene product.