title: Interaction of topoisomerase 1 with the transcribed region of the Drosophila HSP 70 heat shock gene.
abstract: Topoisomerase I cleavage sites have been mapped in vivo on the Hsp70 heat shock gene of Drosophila melanogaster cells using the drug camptothecin. Topoisomerase I cleavage was only observed when the Hsp70 gene was transcriptionally active. Site-specific single-strand DNA cleavage by topoisomerase I was confined to the transcribed region of the Hsp70 gene and occurred on both the transcribed and nontranscribed DNA strands. A number of the single-strand breaks on the complementary DNA strands occurred in close proximity giving rise to double-stranded DNA breaks. Inhibition of heat-induced Hsp70 transcription by either Actinomycin D (Act D) or 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) inhibited topoisomerase I cleavage except at the 5' and to a lesser extent the 3' end of the gene. Camptothecin (100 microM) inhibited transcription of the Hsp70 gene greater than 95%. These results suggest that topoisomerase I is intimately associated with and has an integral part in Hsp70 gene transcription.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Florida College of Medicine, Gainesville 32610.
authors.forename: P E
authors.initials: PE
authors.lastname: Kroeger
authors.forename: T C
authors.initials: TC
authors.lastname: Rowe
mesh_terms: D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D002166:Camptothecin / Q000494:pharmacology; D004247:DNA / Q000187:drug effects; D004249:DNA Damage; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000235:genetics*; D004587:Electrophoresis, Agar Gel; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009693:Nucleic Acid Hybridization; D014158:Transcription, Genetic
chemical_list: D006360:Heat-Shock Proteins; D004247:DNA; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin