A Simple Method to Produce Sub-Nucleosome Complexes of High Purity <i>In Vitro</i>

Abstract

With the identification of increasing number of chromatin modifiers, histone variants, histone post-translational modifications and their cross-talk, it is essential to validate these findings and interactions in vitro for which pure histone complexes are required. Although, the production of such complexes has been described earlier but still it remains a challenge for a non-specialist lab. Here we describe a protocol to quickly obtain large quantities of highly pure histones using bacterial expression system for GST pull-down and reconstitution experiments. In addition, we describe methods to quickly reconstitute and purify H2A/H2B dimers, H3/H4 tetramers and histone octamers for in vitro experiments. We demonstrate that these sub-complexes are properly folded and are hence, true representatives of the actual substrates in vivo . We also show that histones have a propensity to be non-specifically cleaved by proteases. Our results suggest that TEV protease is the most suitable protease while working with histones. The methodology described here should allow researchers to purify histone complexes in three days enabling functional and structural analyses of histone variants, mutants and post-translational modifications.