Negative supercoiling of DNA by eukaryotic DNA topoisomerase II and dextran sulfate.
In the presence of a molar excess of eukaryotic DNA topoisomerase II and an appropriate concentration of dextran sulfate, relaxed closed circular DNA is converted to a negatively supercoiled form. The reaction is dependent on ATP. Neither adenosine 5'-[beta,gamma-imido]-triphosphate nor adenosine 5'-[gamma-thio]triphosphate can substitute for ATP. The negative supercoils formed are relaxed by subsequent addition of DNA topoisomerase I to the supercoiling reaction mixture. Covalent closure of a nicked circular DNA in the presence of DNA topoisomerase II and dextran sulfate but in the absence of ATP causes a small decrease in the linking number. These results suggest that when an appropriate concentration of dextran sulfate is present, the binding of a molar excess of eukaryotic DNA topoisomerase II constrains a small number of negative supercoils in DNA, which in turn generate unconstrained negative supercoils at the expense of ATP.
Okada
K
K
DNA Research Center, National Institute of Genetics, Shizuoka.
Ohta
T
T
Hirose
S
S
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D004250:DNA Topoisomerases, Type II / Q000494:pharmacology*; D004278:DNA, Superhelical / Q000737:chemistry* / Q000187:drug effects; D016264:Dextran Sulfate / Q000494:pharmacology*; D009690:Nucleic Acid Conformation; D012568:Schizosaccharomyces / Q000201:enzymology*; D013950:Thymus Gland / Q000737:chemistry
D004278:DNA, Superhelical; D000255:Adenosine Triphosphate; D016264:Dextran Sulfate; D004250:DNA Topoisomerases, Type II