Characterization of a monoclonal antibody reacting with histone H3

A hybridoma cell line, 1GB3, has been obtained from a fusion between SP/O-Ag 14 myeloma cells and lymphocytes from BALB/c mice immunized with rat liver nuclear proteins. This hybridoma secreted a monoclonal antibody of the IgG2b class which reacted specifically with histone H3 in enzyme-linked immunosorbent assay (ELISA) as well as in immunoblotting and immunodot assays. Stringent test conditions were necessary to eliminate the presence of nonspecific or contaminating reactions with other histones than H3. The monoclonal antibody appears to recognize an epitope situated in the N-terminal residues 20–50 of histone H3; it recognizes this epitope in the octamer aggregate of core histones but not in the core particle.