[Competitive binding of histones to DNA and the problem of chromatin self-assembly]

The competitive binding of histones to DNA in a medium of physiological ionic strength (0.15 M NaCl) and in water was studied by an electrophoretic analysis of histones bound to DNA and retaining their free state in the mixtures of DNA with total histone. In the medium of physiological ionic strength the binding sequences of more and less competitive histone fraction molecules to DNA can be represented as follows: H3+H4, H2a+ +H2b and H3, H4, H2a, H2b and H1, which is indicative of the absence of histone complexes in water and their presence in 0.15 M NaCl, in addition to individual molecules. In water the binding sequences of the histone, molecules to DNA were identical, i. E. H3+H4, H2a, H2b+H1. It was concluded that the non-ionic interaction between the histones bound to DNA determines the discrepancy between the values of histone net charges and their relative affinities for DNA by increasing the correlation between the positively charged amino acid residues of the histones. The relations between the histone competition for DNA and the chromatin self-assembly as well as the reproduction of the specific pattern of gene expression in the cell generation are discussed.