[Electrophoretic study of the heterogeneity of chromatin subunits]

Electrophoretic heterogeneity of chromatin subunits (mononucleosomes) isolated from rat thymus nuclei after mild nuclease digestion has been studied. Just as in the original nuclease hydrolysate of the nuclei and after its fractionation on a Sepharose 4B, mononucleosomes are found to include several fractions (up to four) varying in their protein moieties and sizes of DNA segments Mononucleosomes obtained from the nuclei contain an additional non-histone protein as a minor component. The distribution of rapidly labeled RNA and of newly synthesized DNA among eletrophoretic chromatin fragments has been investigated. Newly synthesized chromatin has a subunit structure typical of the whole chromatin. Rapidly labelled RNA was found in dinucleosomes and mononucleosomes, being predominantly bind to mononucleosome fraction devoid of histone H1.