Testing the effect of histone native chemical ligation on protein binding to di-nucleosomes

Here we examined whether histones H3 and H4 produced using native chemical ligation reaction affect protein binding to di-nucleosomes. To test this we performed a set of affinity purification pull-downs using di-nucleosomes containing the following histones H3 and H4: 1. unmodified ligated histone H3 and recombinant wild type histone H4 (unmod. H3), 2. recombinant wild type histone H3 and ligated unmodified histone H4 (unmod. H4) 3. ligated unmodified histones H3 and H4 (unmod. H3&H4). 4. recombinant wild type histones H3 and H4 (WT) Each pull-down was performed in three replicates. Co-purified proteins were quantified using label-free MS. Note that ligated histones H3 and H4 contain T32C or I29C single amino acid substitutions, respectively, that are introduced by the native chemical ligation procedure. In addition, ligated histone H4 is N-terminally acetylated to mimic its naturally blocked N-terminus.