Studying the Evolution of Histone Variants Using Phylogeny

Histones wrap DNA to form nucleosomes that package eukaryotic genomes. Histone variants have evolved for diverse functions including gene expression, DNA repair, epigenetic silencing, and chromosome segregation. With the rapid increase of newly sequenced genomes the repertoire of histone variants expands, demonstrating a great diversification of these proteins across eukaryotes. In this chapter, we are providing guidelines for the computational characterization and annotation of histone variants. We describe methods to predict the characteristic histone fold domain and list features specific to known histone variants that can be used to categorize newly identified histone fold proteins. We continue describing procedures to retrieve additional related histone variants for comparative sequence analyses and phylogenetic reconstructions to refine the annotation and to determine the evolutionary trajectories of the variant in question.