Proteins in the core histone families, histone H2A and histone H2B represent 2 of the 4 families of histones found in the core of nucleosomes. Histones in the H2A family dimerize with those in the H2B family, then two H2A/H2B dimers can associate with a tetramer containing 2 proteins from the histone H3 family and 2 proteins from the histone H4 family to form the octameric nucleosome core. The octameric complex is the basic unit for eukaryotic DNA packaging. [ ]