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Nuclear distribution of human DNA topoisomerase IIβ: A nuclear targeting signal resides in the 116-residue C-terminal tail

Lookup NU author(s): Dr Ian CowellORCiD, Dr Elaine WillmoreORCiD, Dr David Allen Chalton, Professor Caroline AustinORCiD


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We have analyzed the subcellular distribution of the β isoform of human topoisomerase II using both isoform-specific antisera and an epitope-tagging approach. Previous immunocytochemical studies have yielded differing results with one reporting this isoform to be predominantly nucleolar. Later studies seem to refute this finding, as do our results with isoform-specific antisera reported here. Epitope tagging minimizes potential complications arising from the use of anti-topoisomerase II antisera that may recognize epitopes that are modified or masked in vivo and could lead to misleading results in immunocytochemical studies. A second strength of this approach is that it allowed a comparison with similarly tagged control proteins (derived from the nucleolar transcription factor UBF) that were known to localize unambiguously to the cytoplasmic, nucleoplasmic, or nucleolar compartments. We report that the C-terminal domain of topoisomerase IIβ fused to a β-galactosidase tag localizes to the nucleus (but not the nucleolar compartment) and that this is indistinguishable from the localization of native topoisomerase IIβ detected by isoform-specific antisera. Further analysis revealed that the nuclear localization determinant lies within the 116-residue C-terminal tail of human topoisomerase IIβ.

Publication metadata

Author(s): Cowell IG, Willmore E, Chalton DA, Marsh KL, Jazrawi E, Fisher LM, Austin CA

Publication type: Article

Publication status: Published

Journal: Experimental Cell Research

Year: 1998

Volume: 243

Issue: 2

Pages: 232-240

Print publication date: 15/09/1998

ISSN (print): 0014-4827

ISSN (electronic): 1090-2422


DOI: 10.1006/excr.1998.4150

PubMed id: 9743583


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