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  • Title: Characterization of a topoisomerase-like activity at specific hypersensitive sites in the Drosophila histone gene cluster.
    Author: Villeponteau B.
    Journal: Biochem Biophys Res Commun; 1989 Jul 14; 162(1):232-7. PubMed ID: 2546546.
    Abstract:
    It is well known that treatment of DNA-topoisomerase complexes with SDS induces cleavage of the DNA by trapping a reactive intermediate in which the topoisomerase is covalently linked to the terminal phosphates of the cut DNA. I have used this technique to examine potential topoisomerase binding sites in the histone gene chromatin of Drosophila Kc cells. Treatment of Kc nuclei with SDS induces Mg++-dependent DNA cleavage near the borders of two nuclease-hypersensitive sites located 5' and 3' of histone H4. It is likely that the SDS-induced cleavage at these hypersensitive sites is due to a topoisomerase because protein becomes tightly bound to the ends of the cleaved DNA fragments. Preliminary experiments suggest that a type II topoisomerase may be responsible for the cleavage.
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