[Nucleosomes of active chromatin from sea urchin embryo cells are rich in early histone variants].

By means of selective micrococcal nuclease digestion chromatin from early stages of the sea urchin St. droebachiensis embryogenesis was divided into fractions differing by their transcriptional activity. The electrophoretic analysis of histones at the gastrula stage showed that the transcriptionally active chromatin fraction was enriched with early variants of histone H2A and H1. On the stage of pluteus, when primary cell differentiation is completed, the amount of total histone H1 in this fraction was significantly decreased, however it was enriched in an early alpha variant. It was shown that after mild micrococcal nuclease digestion mononucleosomes, which were mostly derived from active chromatin, were significantly enriched with in vivo labeled early histone variants.