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  • Title: Topoisomerase I interacts with transcribed regions in Drosophila cells.
    Author: Gilmour DS, Pflugfelder G, Wang JC, Lis JT.
    Journal: Cell; 1986 Feb 14; 44(3):401-7. PubMed ID: 3002635.
    Abstract:
    The in vivo distribution of topoisomerase I on specific DNA sequences is determined at high resolution in Drosophila cells using a photo-crosslinking method. Topoisomerase I-DNA adducts are generated by irradiation of intact cells with UV light and then purified by immunoprecipitation with antibody to topoisomerase I. Analyses of the DNA sequences crosslinked to topoisomerase I by blot-hybridization with appropriate DNA probes indicate that topoisomerase I is concentrated on transcribed regions and not on nontranscribed flanking sequences. Like RNA polymerase II, topoisomerase I is recruited to heat-shock genes during the heat-shock response. However, topoisomerase I and RNA polymerase II can interact independently with the transcribed region because different ratios of topoisomerase I and RNA polymerase II are crosslinked to the highly transcribed hsp70 gene and the moderately transcribed copia genes. We hypothesize that topoisomerase I allows topological changes in DNA that are required for transcription.
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