title: Studies on DNA topoisomerase activity during in vitro chromatin assembly.
abstract: The in vitro assembly of chromatin, promoted by the Xenopus cell-free extract (S-150), can be inhibited by oxolinic acid and to a lesser extent by nalidixic acid. Both of these antibiotics have been shown to block the activity of the specialized type II Topoisomerase, bacterial DNA Gyrase. Oxolinic acid induces a DNA cleavage by Micrococcal Nuclease at specific sequences in the multiple cloning vector pGEM-4. Nalidixic acid does not inhibit DNA supercoiling, but does diminish the extent of chromatin formation achieved by the S-150 on circular DNA templates. The Topoisomerase I inhibitor, berenil, does not inhibit extensive chromatin assembly, although it does diminish the level of supercoiling. Taken together, these results suggest that both topoisomerases play a role in the assembly process. Topoisomerase I may catalyze both the introduction of unconstrained supercoils into relaxed DNA and the formation of monosomes, while Topoisomerase II may promote extended chromatin assembly.
authors.affiliation: Department of Biochemistry and Biophysics, University of California, Davis 95616.
authors.forename: J A
authors.initials: JA
authors.lastname: Sekiguchi
authors.forename: E B
authors.initials: EB
authors.lastname: Kmiec
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002843:Chromatin / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004278:DNA, Superhelical / Q000378:metabolism*; D004133:Diminazene / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D009268:Nalidixic Acid / Q000494:pharmacology; D009707:Nucleosomes / Q000187:drug effects / Q000378:metabolism*; D010093:Oxolinic Acid / Q000494:pharmacology; D010957:Plasmids; D014982:Xenopus laevis
chemical_list: D000900:Anti-Bacterial Agents; D000970:Antineoplastic Agents; D002843:Chromatin; D004278:DNA, Superhelical; D009707:Nucleosomes; D009268:Nalidixic Acid; D004264:DNA Topoisomerases, Type I; C003915:diminazene aceturate; D010093:Oxolinic Acid; D004133:Diminazene