title: Identification of a nucleolin binding site in human topoisomerase I.
abstract: DNA topoisomerase I (topo I) is involved in the regulation of DNA supercoiling, gene transcription, and rDNA recombination. However, little is known about interactions between topo I and other nuclear proteins. We used affinity chromatography with a topo I fusion protein to screen U-937 leukemic cell extracts and have identified nucleolin as a topo I-binding protein. Coimmunoprecipitation and other studies demonstrate that the interaction between topo I and nucleolin is direct. Furthermore, deletion analyses have identified the 166-210-amino acid region of topo I as sufficient for the interaction with nucleolin. Since nucleolin has been implicated in nuclear transport and in a variety of transcriptional processes, the interaction with topo I may relate to the cellular localization of topo I or to the known role of this topoisomerase in transcription.
authors.affiliation: Division of Cancer Pharmacology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Bharti
authors.forename: M O
authors.initials: MO
authors.lastname: Olson
authors.forename: D W
authors.initials: DW
authors.lastname: Kufe
authors.forename: E H
authors.initials: EH
authors.lastname: Rubin
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002451:Cell Compartmentation; D004264:DNA Topoisomerases, Type I / Q000737:chemistry* / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism; D016601:RNA-Binding Proteins; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014407:Tumor Cells, Cultured; D000097796:Nucleolin
chemical_list: D004264:DNA Topoisomerases, Type I; D004278:DNA, Superhelical; D009687:Nuclear Proteins; D010750:Phosphoproteins; D016601:RNA-Binding Proteins; D000097796:Nucleolin