期刊
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
卷 306, 期 4, 页码 905-911出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/S0006-291X(03)01077-5
关键词
topoisomerase II alpha; topoisomerase II beta; nuclear export; GFP fusion protein; confocal microscopy; nuclear microinjection; Leu-rich NES
Nuclear localization of topoisomerase Halpha and beta is important for normal cell function as well as being a determinant of tumour cell sensitivity to topoisomerase II-targeting chemotherapeutic agents. However, topoisomerase II is cytoplasmic under certain circumstances, indicating that it may undergo active nuclear export. We have examined the ability of Leu-rich potential nuclear export signal (NES) sequences present in human topoisomerase Halpha and beta to direct the export of a green fluorescent protein-glutathione-S-transferase fusion protein following microinjection into HeLa cell nuclei. Of 12 sequences tested, only one potential NES sequence from the comparable location in each isoform (alphaNES(1018-1028) and betaNES(1034-1044)) was active. Mutation of hydrophobic residues in alphaNES(1018-1028) and betaNES(1034-1044) substantially reduced their nuclear export activity as did leptomycin B treatment of microinjected cells. Our results provide the first evidence of active nuclear export of topoisomerase II and suggest it is mediated by a CRM1-dependent pathway. (C) 2003 Elsevier Science (USA). All rights reserved.
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