From garcinol to barbituric acid derivatives: development of a novel cell-permeable, selective, and noncompetitive inhibitor of KAT3 histone acetyltransferases.

Abstract

Lysine acetylation is among the prominent posttranslational modifications in eukaryotic cells. Protein acetylation level is a consequence of the balance between the opposite activities of protein acetyltransferases (KATs) and deacetylases (KDACs), and its deregulation has been linked to several diseases, including cancer, inflammation and neurodegenerative diseases. At present, only a small number of KATs modulators have been reported and just a few of them show selectivity between KATs isoforms. Among these, a polyisoprenylated benzophenone, garcinol, isolated from Garcinia Indica, is a potent inhibitor of histone acetyltransferases p300 and PCAF. Starting from the garcinol hardly optimizable and not very cell-permeable core structure, we applied a molecular pruning approach and prepared many analogues that were screened for their inhibitory effects using biochemical and biophysical (SPR) assays. Further optimization led to the discovery of the benzylidenebarbituric acid derivative 7h (EML425) as a potent and selective reversible inhibitor of CBP/p300, non-competitive versus both acetyl-CoA and a histone H3 peptide, and endowed with good cell permeability. Furthermore, in human leukemia U937 cells, it induced a marked and time-dependent reduction in the acetylation of lysine H4K5 and H3K9, a marked arrest in the G0/G1 phase and a significant increase in the hypodiploid nuclei percentage