Fig. 1. Effects of retinoids on histone post-translational modifications. P19 cells were treated with 100 nM atRA or 10 ng/ml TSA (33 nM) for the indicated period of time. Ten micrograms of acid-extracted histones were analyzed (A) by 16% SDS–PAGE to ensure equal loading, (B) by AUGE to assess the extent of acetylation of histones and (C) by western blotting using anti-acetylated (K5, K8, K12 and K16) H4, anti-acetylated (K9 and K14) H3 and anti-phosphorylated (S10) H3. The H4 lane contains 2 µg of purified, non-acetylated histone H4.