Proteins and functional properties of chromatin fractions from nuclei of normal liver and experimental hepatomas

In the modern view nuclear skeletal structures (the nuclear matrix) play an extremely important role in the structural organization of chromatin [12]. There is evidence that differences in the degree of compactness of active and inactive chromatin in the nucleus may be due not only to the specific nature of the protein composition, but also to local differences in interconnection between fibrils of deoxyribonucleoprotein (DNP) with protein fibrils of the matrix: The ~topography of diffuse and condensed regions of the nucleus is preserved after removal of both DNA and histone HI from it [i0]. The possibility of fractionating chromatin, based not on choice of conditions of selective degradation of the DNA of active chromatin, but on differences in solubility of DNP fragments having points of attachment to the matrix and not bound with it, is accordingly interesting. This possibility arises because of the fact that after nuclease treatment of a certain intensity (when the mean size of DNA fragments between neighboring double-stranded breaks is definitely less than the size of DNA of a single loop) under conditions of maximal solubility of DNP in the nucleus, chromatin enriched with points of attachment to the nuclear matrix remains in the nucleus [8].