2.11. ELISA Assay to Detect Histone Modifications

The EpiQuik^TM Total Histone Extraction kit (Epigentek, Farmingdale, NY, USA) was used according to the manufacturer to obtain acid extracts containing histones. Different histone modifications were then measured using the following EpiQuik^TM Global Histone Quantification kits (Epigentek): acetylation of lysine 9 of histone H3 (H3K9ac), tri-methylation of lysine 4 of histone H3 (H3K4me3), tri-methylation of lysine 9 of histone H3 (H3K9me3) and tri-methylation of lysine 27 of histone H3 (H3K27me3). The total histone H3 was assessed in order to standardize the results. Total or modified histone H3 was captured in wells coated with anti-histone H3 antibody or one of the modifications. The captured H3 histones could then be detected with a specific detection antibody for each modification, followed by a fluorescence development reagent (fluorescent secondary antibody). The amount of histone was proportional to the fluorescence intensity obtained with a wavelength of 530ex/590em nm.