Human p300 and CBP (CREB binding protein) are highly related transcriptional coactivators. Both proteins have been identified through protein interaction assays. In addition to interacting with a variety of cellular factors and onco-proteins, loss of the wild type CBP alleles in isolated tumors suggests th at CBP/p300 might serve as a tumor suppressor. The C-terminus of p300 contains a histone acetyltransferase (HAT) domain expanded from residues 1195 to 1673, an activation domain (residues 1763-1812) th at interacts with many transcription factors and an SRC-1 domain further down stream of the activation domain. P300 is able to acetylate histones and many other transcription factors, including p53, E2F, TFIIE, and TFIIF etc. implicating diverse roles of p300 in gene regulation.
