The role of p300 in AD is supported by an experimental evidence that the addition of a p300 inhibitor significantly suppresses the expression of presenilin 1 (PS1) and the beta-site amyloid precursor protein cleaving enzyme 1 (BACE1) via a reduced H3 acetylation within their promoter regions [41, 42]. The gene discussed is BACE1; the disease is Alzheimer disease.