[Drosophila melanogaster embryo factor capable of supercoiling circular covalently closed DNA in the presence of core histones H2a, H2b, H3, H4 or protamine].

The Mg2+-dependent factor capable of introducing the superhelical turns into circular closed DNA in the presence of core histones H2a, H2b, H3, H4 or protamine in solution at physiological conditions has been isolated from Drosophila melanogaster embryos. The factor does not work with histone H1, cytochrome c, poly-L-lysine or tetralysine. It is assumed that the factor is responsible for folding of core histones into nucleosomes.