title: Histone H1 inhibits eukaryotic DNA topoisomerase I.
abstract: Histone H1 inhibits the catalytic activity of topoisomerase I in vitro. The relaxation activity of the enzyme is partially inhibited at a molar ratio of one histone H1 molecule per 40 base pairs (bp) of DNA and completely inhibited at a molar ratio of one histone H1 molecule per 10 base pairs of DNA. Increasing the amount of enzyme at a constant histone H1 to DNA ratio antagonizes the inhibition. This indicates that topoisomerase I and histone H1 compete for binding sites on the substrate DNA molecules. Consistent with this we show on the sequence level that histone H1 inhibits the cleavage reaction of topoisomerase I on linear DNA fragments.
authors.affiliation: Division of Biology, University of Konstanz, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Richter
authors.forename: M
authors.initials: M
authors.lastname: Kapitza
mesh_terms: D000818:Animals; D002417:Cattle; D004278:DNA, Superhelical / Q000378:metabolism; D006367:HeLa Cells; D006657:Histones / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D009710:Nucleotide Mapping; D010957:Plasmids; D013379:Substrate Specificity; D013950:Thymus Gland / Q000201:enzymology; D059004:Topoisomerase I Inhibitors
chemical_list: D004278:DNA, Superhelical; D006657:Histones; D059004:Topoisomerase I Inhibitors