Regulation of the cellular prion protein gene expression depends on chromatin conformation

Conversion of the normal cellular prion protein (PrPc), whose physiological function is still under investigation, to an infectious form called prion is the cause of some neurodegenerative diseases. Therefore, the elucidation of PrPc gene regulation is important both to define a strategy to control the infection and to better understand PrPc function. We cloned the rat PrPc gene promoter region into a luciferase reporter vector, transfected C6 and PC-12 cells, and isolated clones with stable enzyme expression. The dependence of chromatin conformation on PrPc promoter activity was evaluated using the histone deacetylase inhibitor, trichostatin A, which was able to highly increase not only promoter activity but also PrPc mRNA and protein levels. The phorbol ester (12-O-tetradecanoylphorbol-13-acetate) and cAMP poorly induced promoter activity; retinoic acid decreased it by 50%, whereas nerve growth factor and dexamethasone had no effect. When 12-O-tetradecanoylphorbol-13-acetate or cAMP but not retinoic acid was associated with trichostatin A, a potentiation of the primary effects was observed. These new data indicate that PrPc gene regulation is highly dependent on disruption of chromatin fiber assembly, which allows some ubiquitous transcription factors accession to specific DNA elements.