HISTONE POST-TRANSLATIONAL MODIFICATIONS DETERMINED BY HIGH-PRESSURE LIQUID CHROMATOGRAPHY AND MASS SPECTROMETRY

The nucleosome is the basic structural unit of eukariotic chromosomes and consists of a DNA molecule associated with a histone octamer comprised of pairs of the core histones H2A, H2B, H3 and H4. The nucleosomes are joined by linker DNA and histone1 to form chromatin. Histones play an important role in transcription, DNA replication, DNA repair and recombination. Post-translational modification of specific residues in the core histones (acetylation, methylation, phosphorylation, etc.) has been demonstrated to be critical to their regulatory function. In particular acetylation is a very specific phenomenon with various isoforms playing distinct roles. Increased acetylation is generally correlated with transcriptionally active or poised genes. Histone deacetylases’ inhibitors (short chain fatty acids, such as sodium butyrate, hydroxamic acids such as thrichostatin A) have been described as potential cancer therapeutics in a variety of preclinical studies. Inhibitors’ treatment of cells resulted in the increase of highly acetylated isoforms of the histones, which affect gene expression, cell differentiation and apoptosis. It is here described the application of reversed-phase high-pressure liquid chromatography under gradient conditions and mass spectrometry (LC-MS) to analyse global modification levels of core histones.