Acetylation of estrogen receptor alpha by p300 at lysines 266 and 268 enhances the deoxyribonucleic acid binding and transactivation activities of the receptor

Using a variety of biochemical and cell-based approaches, we show that estrogen receptor alpha (ERalpha) is acetylated by the p300 acetylase in a ligand- and steroid receptor coactivator-dependent manner. Using mutagenesis and mass spectrometry, we identified two conserved lysine residues in ERalpha (Lys266 and Lys268) that are the primary targets of p300-mediated acetylation. These residues are acetylated in cells, as determined by immunoprecipitation-Western blotting experiments using an antibody that specifically recognizes ERalpha acetylated at Lys266 and Lys268. The acetylation of ERalpha by p300 is reversed by native cellular deacetylases, including trichostatin A-sensitive enzymes (i.e. class I and II deacetylases) and nicotinamide adenine dinucleotide-dependent/nicotinamide-sensitive enzymes (i.e. class III deacetylases, such as sirtuin 1). Acetylation at Lys266 and Lys268, or substitution of the same residues with glutamine (i.e. K266/268Q), a residue that mimics acetylated lysine, enhances the DNA binding activity of ERalpha in EMSAs. Likewise, substitution of Lys266 and Lys268 with glutamine enhances the ligand-dependent activity of ERalpha in a cell-based reporter gene assay. Collectively, our results implicate acetylation as a modulator of the ligand-dependent gene regulatory activity of ERalpha. Such regulation is likely to play a role in estrogen-dependent signaling outcomes in a variety of estrogen target tissues in both normal and pathological states.