DOI: 10.1002/cbic.200900721 The Identification of a Novel Natural Activator of p300 Histone Acetyltranferase Provides New Insights into the Modulation Mechanism of this Enzyme Fabrizio Dal Piaz,* [a] Alessandra Tosco, [a] Daniela Eletto, [a] Anna L. Piccinelli, [a] Ornella Moltedo, [a] Silvia Franceschelli, [a] Gianluca Sbardella, [a] Paolo Remondelli, [a] Luca Rastrelli, [a] Loredana Vesci, [b] Claudio Pisano, [b] and Nunziatina De Tommasi [a] Introduction The acetylation of proteins is a dynamic event that involves the enzymatic activity of histone acetyltransferases (HATs) and histone deacetylases (HDACs). HATs primarily acetylate (and prevent positive charges from forming on) the e-amino groups of specific lysines in histones, as well as in transcription factors (i.e., p53) and other nuclear proteins (i.e., a-tubulin). As a con- sequence, HATs modulate gene transcription, nucleosome as- sembly, and DNA repair. Altered HAT and HDAC function leads to several diseases, ranging from cancer to neurodegenerative disorders ; [1–3] because not all such diseases involve hypoacety- lation, but also hyperacetylation, compounds able to enhance or repress histone acetyltransferase (HATs) activity could be promising therapeutic agents. Several members of the HAT family have been identified so far, and many of them, that is, p300/CBP, [4, 5] TAFII250, [6] and SRC-1, [7] function as transcriptional coactivators. p300 plays a pivotal role in a variety of cellular processes including cell cycle control, differentiation, and apoptosis. It is a potent histone acetyltransferase that can acet- ylate core histones within nucleosomes as well as free histone forms, and mutations in the p300 gene are associated with different human cancers and other human diseases. [8, 9] This protein is recruited to the chromatin template through direct interactions with the transcriptional activator proteins, thus en- hancing transcription by acetylation of nucleosomal histones located at the promoter regions of target genes. [10] Significant progress in the field of cancer therapy has been made by the use of HDAC inhibitors as antineoplastic agents; in fact, a number of HDAC inhibitors are currently undergoing clinical evaluation for efficacy in the treatment of human tumors. [11–15] In contrast, HAT enzymes have been less investi- gated as therapeutic targets and, as a matter of fact, only a small number of HAT modulators have been reported so far, the first being Lys-CoA and H3-CoA-20, selective for p300 and PCAF, respectively. [16] Their main disadvantages were low cell permeability and metabolic instability. Some natural compounds, such as anacardic acid, curcumin, and garcinol were described lately as PCAF and p300 inhibi- tors. [17] Garcinol, a polyisoprenylated benzophenone isolated from Garcinia indica fruit rind, was found to affect both in vitro and in vivo enzymatic activity of HATs, and inhibits the HAT activity-dependent chromatin transcription and downregulates global gene expression. [18] Moreover, garcinol was also report- ed as a cell-permeable HAT inhibitor and a potent antiapoptot- ic agent in tests with the HeLa cell line. [19] These observations prompted us to study the effects that several polyisoprenylated benzophenone derivatives (PBDs) containing garcinol-like structural features isolated from natu- ral sources have on p300 HATactivity. Structurally, PBDs feature Many severe human pathologies are related to alterations of the fine balance between histone acetylation and deacetyla- tion; because not all such diseases involve hypoacetylation, but also hyperacetylation, compounds able to enhance or repress the activities of histone acetyltransferases (HATs) could be promising therapeutic agents. We evaluated in vitro and in cell the ability of eleven natural polyisoprenylated benzophe- none derivatives to modulate the HAT activity of p300/CBP, an enzyme that plays a pivotal role in a variety of cellular process- es. Some of the tested compounds bound efficiently to the p300/CBP protein : in particular, guttiferone A, guttiferone E and clusianone inhibit its HAT activity, whereas nemorosone showed a surprising ability to activate the enzyme. The ability of nemorosone to penetrate cell membranes and modulate histone acetylation into the cell together with its high affinity for the p300/CBP enzyme made this compound a suitable lead for the design of optimized anticancer drugs. Besides, the stud- ies performed at a cellular and molecular level on both the inhibitors and the activator provided new insights into the modulation mechanism of p300/CBP by small molecules. [a] Dr. F. Dal Piaz, Dr. A. Tosco, Dr. D. Eletto, Dr. A. L. Piccinelli, Dr. O. Moltedo, Dr. S. Franceschelli, Prof. G. Sbardella, Prof. P. Remondelli, Prof. L. Rastrelli, Prof. N. De Tommasi Dipartimento di Scienze Farmaceutiche, Università degli Studi di Salerno Via Ponte Don Melillo 1, 84084 Fisciano (SA) (Italy) Fax: (+ 39) 089969602 E-mail : fdalpiz@unisa.it [b] Dr. L. Vesci, Dr. C. Pisano Research and Development Department Sigma-Tau, Via Pontina Km 30,400, 00040 Pomezia, Roma (Italy) 818  2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ChemBioChem 2010, 11, 818 – 827