Fig 4.

Drug-induced acetylation of histone and nonhistone proteins in NB4 cells. (A) Cells were incubated for 6 hrs without/with 2 μM (S)-2 or (R)-2 or 4, and then processed by Western blot and immunostained for acetylated H3/H4; H3/H4 were the loading controls. Cell extracts were also analysed by immunoblotting for (B) acetylated forms of nonhistone proteins α-tubulin and p53 after 6 and 24 hrs of treatment, respectively; α-tubulin and p53 were used as the reference proteins. (C) Drug-induced inhibition of human recombinant HDAC1 and HDAC6 activity was determined by a fluorimetric cell-free assay (S2); IC₅₀ values were from a typical experiment out of three.