Small-Molecule Inhibitors of Histone Acetyltransferase Activity: Identification and Biological Properties

Starting from a yeast phenotypic screening performed on 21 compounds, we described the identification of two small molecules (9 and 18) able to significantly reduce the S. cerevisiae cell growth, thus miming the effect of GCN5 deletion mutant. Tested on a GCN5-dependent gene transcription assay, compounds 9 and 18 gave a high reduction of the reporter activity. In S. cerevisiae histone H3 terminal tails assay, the H3 acetylation levels were highly reduced by treatment with 0.6−1 mM 9, while 18 was effective only at 1.5 mM. In human leukemia U937 cell line, at 1 mM 9 and 18 showed effects on cell cycle (arrest in G1 phase, 9), apoptosis (9), and granulocytic differentiation (18). When tested on U937 cell nuclear extracts to evaluate their histone acetyltransferase (HAT) inhibitory action, both compounds were able to reduce the enzyme activity when used at 500 μM. Another quinoline, compound 22, was synthesized with the aim to improve the activity observed with 9 and 18. Tested in the HAT assay, 22 was able...