Histone H2A and H2B are the core components of the nucleosome. H2A and H2B assemble H2A/H2B dimer, and two H2A/H2B dimers combine with H3/K4 tetramer to form histone octamer. The histone octamer is wrapped around by 146 bp DNA to assemble a nucleosome, which is the basic structural unit of chromatin in vivo.
