Fluorescence-labeled octapeptides as substrates for histone deacetylase

The determination of histone deacetylase (HDAC) activity and the screening of potential inhibitors is gaining increasing importance due to the involvement of HDAC in transcription regulation. The level of histone acetylation can be modulated by HDAC inhibitors resulting in differentiation and/or apoptosis in cancer cells. We have previously reported the development of a nonisotopic assay for HDAC using a fluorescent derivative of epsilon -acetyl lysine. Here we report fluorescein-labeled octapeptides which are substrates for HDAC that bear closer resemblance to the native substrate. HPLC with fluorescence detection is successfully applied to the analysis of the time- and site-dependent deacetylation. LC-MS analyses are used to confirm the findings. The observed selectivity toward one of two possible deacetylation sites might result from steric hindrance by the label but the methodology presented here could be applied to similar larger peptides which might be improved tools to characterize HDAC site selectivity in vitro.