[Stages of assembly and structural forms of histone oligomers-- (H2A-H2B) dimer, (H3-H4)2 tetramer and (H3-H4-H2A-H2B)2 octamer].

The process of dimer (H2A-H2B), tetramer (H3-H4)2 and octamer (H3-H4-H2A-H2B)2 formation was analyzed by the methods of gel-filtration and differential spectrophotometry. Histone octamer with the parameters most close to the native ones is established to be reconstructed only from denaturated monomers at neutral pH. The necessary condition for formation of histone octamer is the stage of tetramer (H3-H4)2 and (H2A-H2B) formation. Histone H3 with intramolecular disulphide bond (formula: see text) does not form tetramer (H3-H4)2 and is not a part of octamer. When passing through the dimer (H3-H4) stage it produces nonspecific high-molecular aggregates. Structural changes preceding the formation of histone octamer may play a significant role for transition of chromatin and nucleosomes into the transcription-active, repressed and other states.