Sequence sensitivity of histone binding

The nucleotide sequence selectivity of histone binding has been measured by thermal denaturation of reconstituted nucleoproteins. When DNAs of different average base compositions competed for the binding of purified histone fractions during in vitro reconstitutions in the presence of salt and urea, a decreasing $\text{(A + T)-binding}$ preference was observed following the order $\text{H}\text{1 >}\text{H}\text{2}\text{B}\text{>}\text{H}\text{5 >}\text{H}\text{2}\text{A}\text{> [}\text{H}\text{2}\text{A}\text{+}\text{H}\text{2}\text{B}\text{] > [}\text{H}\text{2}\text{A}\text{+}\text{H}\text{2}\text{B}\text{+}\text{H}\text{3 +}\text{H}\text{4]}$, $\text{[}\text{H}\text{1 + (}\text{H}\text{2}\text{A}\text{+}\text{H}\text{2}\text{B}\text{+}\text{H}\text{3 +}\text{H}\text{4)}{}_2\text{]}$. Nucleoprotein complexes formed under conditions shown to yield more physiologically comparable nucleosome structures revealed a minimal $\text{(A + T)-binding}$ preference. These results suggest that homotypic and heterotypic histone interactions decreased the nucleotide sequence selectivity of nucleosome binding.