title: Drosophila DNA topoisomerase I is associated with transcriptionally active regions of the genome.
abstract: The distribution of DNA topoisomerase I within Drosophila polytene chromosomes was observed by immunofluorescent staining with affinity-purified antibodies. The enzyme is preferentially associated with active loci, as shown by prominent staining of puffs. The heat shock loci 87A-87C are stained after, but not before, heat shock induction. A detailed comparison of the distribution of topoisomerase I with that of RNA polymerase II reveals a similar, although not identical, pattern of association. Topoisomerase I is also found in association with the nucleolus, the site of transcription by RNA polymerase I.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002466:Cell Nucleolus / Q000502:physiology; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D002875:Chromosomes / Q000648:ultrastructure; D004264:DNA Topoisomerases, Type I / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics*; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics; D012319:RNA Polymerase II / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D002868:Chromosomal Proteins, Non-Histone; D006360:Heat-Shock Proteins; D012319:RNA Polymerase II; D004264:DNA Topoisomerases, Type I