HBP1 is a sequence-specific DNA-binding transcription factor. It is involved in many biological processes. It was reported that HBP1 binds to p16(INK4A) promoter and activates p16(INK4A) expression. We found that trichostatin A (TSA), an inhibitor of HDAC (histone deacetylase), induces p16(INK4A) expression in an HBP1-dependent manner. HBP1 activates or represses the expression of some specific genes during cell growth and differentiation. HBP1 was acetylated by p3/CBP in two regions: repression domain (K297/35/37) and P domain (K171/419). HBP1 acetylation after TSA treatment was confirmed by immunoprecipitation assay. HBP1 interacted with histone acetyltransferase p3 and CREB-binding protein (CBP) and also recruited p3/CBP to p16(INK4A) promoter. HBP1 acetylation at K419 plays an important role in HBP1-induced p16(INK4A) expression.