Articles Rearrangement of Nucleosomal Components by Modification of Histone Amino Groups. Structural Role of Lysine Residues?

ABSTRACT: Modification of nucleosomal particles from chicken erythrocytes with the reagents for protein amino groups acetic and dimethylmaleic anhydrides causes a rearrangement of nucleosomal components. Treatment with both reagents is accompanied by liberation of free DNA and formation of residual particles with anomalous histone composition. The residual particles obtained with acetic anhydride contain an excess of histones corresponding to the free DNA produced. In contrast, dimethylmaleic anhydride causes release of hi-stones H1, H5, H2A and H2B and formation of residual particles deficient in these histones but containing an excess of H3 and H4 corresponding to the liberated DNA. Regen-Double-stranded DNA is wrapped around a histone octamer to form the nucleosomal core which is the basic structure present in chromatin (McGhee & Felsenfeld, 1980; Sperling & Wachtel, 1981). The forces that distort the DNA double helix to produce a condensed superhelical structure appear to be essentially electrostatic. The negatively charged phosphate groups of DNA would interact with the positively charged amino acid residues, lysine and arginine, of the core histones to induce the nucleosomal DNA structure. Arginine-rich histones, H3 and H3, are electrostatically more strongly bound to DNA than the lysine-rich pair, H2A and H2B, the two first histones being essential for the organization of DNA structure in nucleosomes (Camerini-Otero et al., 1976; Sollner-Web