An region upstream of the gene promoter for the beta-amyloid precursor protein interacts with proteins from nuclear extracts of the human brain and PC12 cells.

The amyloid beta-protein (Abeta) is the major proteinaceous component of the amyloid deposits that accumulate extracellularly in the brain of Alzheimer's disease (AD). Abeta is generated proteolytically from a larger beta-amyloid precursor protein (betaAPP). The apparent overexpression of the betaAPP gene in certain areas of AD brains indicate that abnormalities in gene regulation might be an important factor in AD. Here, I report that an upstream regulatory element (URE) located between -2257 to -2234 base pair (bp) of the human betaAPP promoter may interact with a novel protein(s) as determined by a gel shift assay. To determine whether this novel protein is related to an already characterized transcription factor, a gel shift assay was performed using various specific competitors in human neuroblastoma and rat pheochromocytoma (PC12) cells. The labeled URE probe could interact with a distinct nuclear factor which was not competed by the oligonucleotides specific for the different transcription factors, AP1, AP2, AP3, GRE, Oct1, NF1 and NF-kappaB. Alternatively the specific protein band(s) detected with either the labeled NF-kappaB or NF1 probe could not be competed out with an excess of unlabeled URE. To determine if such a band could be detected in human brain tissue samples, a gel shift assay from the nuclear extracts of the human brain was performed. A distinct URE-specific nuclear factor was detected in different regions of the brain as well. To determine the size of the protein(s) that were specifically bound in the DNA-protein complexes, Southwestern blotting was performed. Using the URE probe, two major protein bands of approximately 53 and 116 kDa were detected in PC12 nuclear extracts. These results suggest that the protein factor(s) interacting with URE is not related to the known transcription factors tested, and that the protein is expressed in certain cell types and different regions of the human brain.