Structural alteration in alternating adenine-thymine sequences in positively supercoiled DNA.
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.
McClellan
J A
JA
Department of Biochemistry, The University, Dundee, U.K.
Lilley
D M
DM
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
D004278:DNA, Superhelical; D003609:Dactinomycin; D000225:Adenine; D009993:Osmium Tetroxide; D013941:Thymine