DNA-binding protein Pur alpha and transcription factor YY1 function as transcription activators of the neuron-specific FE65 gene promoter.

Fe65 is an adaptor protein that interacts with the Alzheimer beta-amyloid precursor protein and is expressed mainly in the neurons of several regions of the nervous system. The FE65 gene has a TATA-less promoter that drives an efficient transcription in cells showing a neuronal phenotype, whereas its efficiency is poor in non-neuronal cells. A short sequence encompassing the transcription start site contains sufficient information to drive the transcription in neuronal cells but not in non-neural cells. Electrophoretic mobility-shift assays performed with rat brain nuclear extracts showed that three major DNA-protein complexes, named BI, BII and BIII, are formed by the FE65 minimal promoter. The proteins present in complexes BI and BII were purified from bovine brain; internal microsequencing of the purified proteins demonstrated that they corresponded to the previously isolated single-stranded-DNA-binding protein Pur alpha, abundantly expressed in the brain. In Chinese hamster ovary (CHO) cells, where the efficiency of FE65 promoter is very low, transient expression of Pur alpha increased the transcription efficiency of the FE65 minimal promoter. By using oligonucleotide competition and a specific antibody we demonstrated that the transcription factor YY1 is responsible for the formation of complex BIII. Also in this case, the transient expression of the YY1 cDNA in CHO cells resulted in an increased transcription from the FE65 minimal promoter. The absence of any co-operative effect when CHO cells were co-transfected with both YY1 and Pur alpha cDNA species suggests that two different transcription regulatory mechanisms could have a role in the regulation of the FE65 gene.