Histone H2B is one of the four histones, along with H2A, H3 and H4, which forms the eukaryotic nucleosome core.Histone H2B is a small, highly conserved nuclear protein that, together with 2 molecules each of histones H2A, H3and H4, forms the eukaryotic nucleosome core [<cite idref="PUB00004388"/>]; the nucleosome octamer winds ~146 DNA base-pairs.