title: Visualization of unconstrained negative supercoils of DNA on polytene chromosomes of Drosophila.
abstract: Bulk DNA within the eukaryotic genome is torsionarily relaxed. However, unconstrained negative supercoils of DNA have been detected in few local domains of the genome through preferential binding of psoralen. To make a genome-wide survey for such domains, we introduced biotinylated psoralen into Drosophila salivary glands and visualized it on polytene chromosomes with fluorescent streptavidin. We observed bright psoralen signals on many transcriptionally active interbands and puffs. Upon heat shock, the signals appeared on heat-shock puffs. The signals were resistant to RNase treatment but disappeared or became faint by previous nicking of DNA or inhibition of transcription with alpha-amanitin. These data show that transcription-coupled, unconstrained negative supercoils of DNA exist in approximately 150 loci within the interphase genome.
authors.affiliation: Department of Developmental Genetics, National Institute of Genetics, SOKENDAI, 1111 Yata, Mishima, Shizuokaken 411-8540, Japan.
authors.forename: Kuniharu
authors.initials: K
authors.lastname: Matsumoto
authors.forename: Susumu
authors.initials: S
authors.lastname: Hirose
mesh_terms: D000546:Amanitins / Q000378:metabolism; D000818:Animals; D019921:Biotinylation; D015139:Blotting, Southern; D002875:Chromosomes / Q000648:ultrastructure*; D004247:DNA / Q000378:metabolism; D004278:DNA, Superhelical; D004305:Dose-Response Relationship, Drug; D004331:Drosophila melanogaster; D005363:Ficusin / Q000378:metabolism; D016678:Genome; D006358:Hot Temperature; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D014158:Transcription, Genetic; D014965:X-Rays
chemical_list: D000546:Amanitins; D004278:DNA, Superhelical; D012313:RNA; D004247:DNA; D012260:Ribonucleases; D005363:Ficusin