Proteome analysis of protein partners to nucleosomes containing canonical H2A or the variant histones H2A.Z or H2A.X.

Although the existence of histone variants has been known for quite some time, only recently are we grasping the breath and diversity of the cellular processes in which they are involved. Of particular interest are the two variants of histone H2A, H2A.Z and H2A.X, because of their roles in regulation of gene expression and in DNA double-strand break repair, respectively. We hypothesize that nucleosomes containing these variants may perform their distinct functions by interacting with different sets of proteins. Here we present our proteome analysis aimed at identifying protein partners that interact with nucleosomes containing H2A.Z, H2A.X, or their canonical H2A counterpart. Our development of a nucleosome-pull down assay and analysis of the recovered nucleosome-interacting proteins by mass spectrometry allowed us to directly compare nuclear partners of these variant-containing nucleosomes to those containing canonical H2A. To our knowledge, our data represent the first systematic analysis of the H2A.Z and H2A.X interactome in the context of nucleosome structure.