PARP inhibition up-regulates global HDAC activity.

(A) Nuclear extracts from NIH3T3 cells, treated with the inhibitor PJ34 (5 μM) for 1 h, and assayed for global HAT activity. Histograms indicate colorimetric quantification, through an ELISA-like reaction, of HAT activity in treated cells relative to untreated (NT, value ~1). Error bars indicate the standard deviation of data obtained from three independent experiments. (B) Same as in (A) but the assay was for global HDAC activity. *p ≤ 0.05. (C) The same nuclear extracts as in (A) and (B) were run on a 15% SDS-PAGE, and probed with anti-acetyl-histone H3 and anti-C-terminal of H3 antibodies to measure the relative level of H3 acetylation. Error bars indicate the standard deviation of data obtained from three independent experiments. (D) Same as in (C) but hybridisation was performed with anti-acetyl-histone H4 and anti-C-terminal of H4 antibodies to measure the relative level of H4 acetylation.