Bipartite nuclear localization signals in the C terminus of human topoisomerase IIα
Bipartite nuclear localization signals in the C terminus of human topoisomerase IIα
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DOI：
10.1006/excr.1997.3805
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发表时间：
1997-12-15
影响因子：
3.7
通讯作者：
Cole, SPC
中科院分区：
文献类型：
--
作者：
Mirski, SEL;Gerlach, JH;Cole, SPC
DNA 拓扑异构酶 II α 是几种重要化疗药物的细胞内靶标，并且已经描述了耐药人类肿瘤细胞系，其中该酶 C 近端区域的缺失与其细胞质定位相关。我们使用修改后的基序定义在该区域鉴定了多个潜在的二分核定位信号（NLS）序列，并且在本研究中，我们将其中的五个表达为与β-半乳糖苷酶的融合蛋白。仅一个序列（涵盖氨基酸 1454 至 1497）就足以引起强烈的核定位。随后的突变分析表明，该 NLS 序列是二分的，并且两个结构域都包含两个以上的碱性氨基酸。用谷氨酰胺取代第二个碱性结构域中位置 1492 的赖氨酸残基导致融合蛋白无效地定位到细胞核，表明该结构域中的所有三个碱性残基都是必需的。我们的结果证实，需要更广泛的定义来检测多肽序列中所有潜在的二分 NLS 基序，尽管功能测试对于鉴定那些实际上能够指导核定位的序列仍然至关重要。 (C) 1997 年学术出版社。
DNA topoisomerase II alpha is the intracellular target for several important chemotherapeutic agents, and drug-resistant human tumor cell lines have been described in which deletions in the C-proximal region of this enzyme are associated with its cytoplasmic localization. We have identified multiple potential bipartite nuclear localization signal (NLS) sequences in this region using a modified definition of the motif, and in the present study, we have expressed five of these as fusion proteins with beta-galactosidase. Only one sequence (spanning amino acids 1454 to 1497) was sufficient to cause strong nuclear localization. Subsequent mutation analyses indicated that this NLS sequence was bipartite and that both domains contain more than two basic amino acids. Substitution of the lysine residue at position 1492 in the second basic domain with glutamine resulted in a fusion protein that localized inefficiently to the nucleus, indicating that all three basic residues in this domain are necessary. Our results confirm that a broader definition is required to detect all potential bipartite NLS motifs in a polypeptide sequence, although functional tests are still essential for identification of those sequences actually capable of directing nuclear localization. (C) 1997 Academic Press.