Soluble and insoluble rat liver chromatin is different in structure and protein composition

Rat liver chromatin has been fractionated by different solubility in solvents of 155 mM ionic strength in soluble S and insoluble I-chromatin. Histone H1 content is lower in S as compared to I-chromatin. The HMG1/2 nonhistone proteins are observed in S-chromatin and in the nuclear pelleted residue from the chromatin isolation procedure, but no amount can be detected in I-chromatin. Thermal denaturation profiles and CD-spectra are different for S and I-chromatin indicating distinct interactions between DNA and proteins in the chromatin molecules. Both effects, differing protein content and distinct DNA-protein interactions, can be correlated with solubility and insolubility being the result of charge-charge interactions between chromatin molecules and ionic components of the solvent.