Dk. Lahiri et al., Promoter activity of the beta-amyloid precursor protein gene is negativelymodulated by an upstream regulatory element, MOL BRAIN R, 71(1), 1999, pp. 32-41
Alzheimer's disease (AD) is characterized by the aggregation of the amyloid
beta-peptide (A beta) which is generated from a larger beta-amyloid precur
sor protein (beta APP). An overexpression of the beta APP gene in certain a
reas of the AD brain has been suggested to be an important factor in the ne
uropathology of AD. Here we have further characterized an upstream regulato
ry element (URE) located between - 2257 and - 2234 of the human beta APP pr
omoter. In addition to its location in the promoter, BLAST search reveals t
hat URE is present in several introns of the beta APP gene and is also dete
cted in many other genes. For functional studies, two promoter regions were
cloned upstream of the reporter gene, chloramphenicol acetyl transferase (
CAT): (i) ph beta E-B - the plasmid that contains the human (h) promoter re
gion (-2832 to + 101) including URE, and (ii) prh beta E-B - the plasmid th
at contains the rhesus (rh) promoter region excluding URE as it lacks a 270
bp region of the h beta APP promoter (-2435 to -2165). Transient transfect
ion studies indicate that ph beta E-B displayed significantly less CAT-prom
oter activity than prh beta E-B in C6, PC12 and SK-N-SH cells. To determine
the role of URE in a heterologous promoter, a p beta URE construct was mad
e by subcloning URE in an enhancerless promoter vector pCATP. The p beta UR
E-CAT construct displayed threefold to fourfold less promoter activity than
pCATP when different cell lines were transfected with the plasmids. URE in
teracts with a novel protein(s) as determined by the electrophoretic mobili
ty shift assay (EMSA). Although the core DNA region of URE resembles with t
he NF-kB element, URE-binding protein is not related to the NF-kB transcrip
tion factor. When EMSA was performed with specific competitors in different
cell lines, the labeled URE probe was not competed by the oligonucleotides
specific for either the AP3, NF-1 or NF-kB transcription factor. The migra
tion of the URE-protein complex was different from the NF-kB-protein comple
x in the EMSA gel. A distinct URE-specific nuclear factor was also detected
in frontal cortex of a normal human brain. These results suggest that the
URE region acts as a repressor element. that the URE-binding protein is not
related to the known transcription factors tested, and that the protein is
present in astrocytic, neuroblastoma, PC12 cells and in the human brain. (
C) 1999 Elsevier Science B.V. All rights reserved.