Ultraviolet light induced preferential crosslinking of histone H3 to DNA in chromatin and nuclei of chicken erythrocytes

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Abstract
Histones were cross-linked to DNA in chicken erythrocyte nuclei and chromatin by using UV light irradiation at 254 nm. Following irradiation, cross-linked histone-DNA adducts were isolated and purified by hydroxylapatite chromatography, and the DNA component was subjected to acid hydrolysis. Of several hydrolysis techniques investigated, trichloroacetic hydrolysis of the DNA component of the adducts was found to be most effective. Histones isolated from hydrolyzed histone-DNA adducts were characterized by gel electrophoresis and fingerprint analysis. No histone-histone protein adducts were observed. All histone fractions cross-link DNA in nuclei or chromatin by using the technique employed, but with different propensities. The order of observed cross-linking, deduced from kinetic experiments, is H1 + H5, H3 > H4 > H2A .mchgt. H2B. The preferential binding of the core histone H3, as compared to the other core histones, is discussed in light of recent data concerning histone-DNA interactions and nucleosome structure. The use of the UV light technique as a conformational probe to study chromatin is also discussed.