title: Structural alteration in alternating adenine-thymine sequences in positively supercoiled DNA.
abstract: An alternating adenine-thymine tract in a relaxed closed circular plasmid was found to become strongly reactive to osmium tetroxide in the presence of actinomycin D. We suggest that this is due to a local overwinding of the alternating tract as a result of positive supercoiling induced by intercalation of the antibiotic at GpC sequences elsewhere in the DNA. We have previously shown that (A.T)n sequences undergo a local underwinding in response to negative supercoiling, and it appears that such sequences are especially torsionally deformable in both directions.
authors.affiliation: Department of Biochemistry, The University, Dundee, U.K.
authors.forename: J A
authors.initials: JA
authors.lastname: McClellan
authors.forename: D M
authors.initials: DM
authors.lastname: Lilley
mesh_terms: D000225:Adenine; D001483:Base Sequence; D004278:DNA, Superhelical / Q000737:chemistry* / Q000187:drug effects; D003609:Dactinomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009993:Osmium Tetroxide / Q000494:pharmacology; D010957:Plasmids; D013941:Thymine
chemical_list: D004278:DNA, Superhelical; D003609:Dactinomycin; D000225:Adenine; D009993:Osmium Tetroxide; D013941:Thymine