Preparing semisynthetic and fully synthetic histones h3 and h4 to modify the nucleosome core.

The purpose of this chapter is to provide practical chemical ligation procedures to prepare histone proteins suitable for the reconstitution of nucleosomes with specific posttranslational modifications in the nucleosome core. Detailed methods are described for the efficient preparation of semisynthetic histones H3 and H4 with modifications near the C-terminus of the proteins by expressed protein ligation and desulfurization. Additionally, we present optimized protocols for solid phase peptide synthesis combined with sequential native chemical ligation to generate fully synthetic modified histone H3, here in the context of H3 lysine 56 acetylation (H3K56ac).