Human Antinuclear Autoantibodies Crossreacting with the Plasma Membrane and the N-Terminal Region of Histone H2B

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Abstract
A subset of human antinuclear autoantibodies (denoted X-ANA) with affinity for mononucleosomes crossreacts with an antigen in the plasma membrane of viable leukocytes. The nature of the nuclear antigen recognized by these antibodies was studied in detail. In immunoblot experiments, it was shown that X-ANA recognizes the core histone H2B, but not the other histones. By using synthetic peptides corresponding to different parts of the core histones as antigens in ELISA, it was shown that X-ANA reacts with the N-terminal residues 6–18 of H2B. The binding of X-ANA to the synthetic 6–18 H2B peptide used as solid-phase antigen in ELISA was inhibited by nucleosomes and by the 6–18 H2B peptide but not by free H2B. These observations agree with earlier suggestions that the N-terminal tail of H2B is located at the surface of the nucleosome and indicate that the native structure of monomeric H2B is different from its structure when complexed within the nucleosomes.