Dimerization and nuclear localization of Ku proteins
Dimerization and nuclear localization of Ku proteins
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DOI：
10.1074/jbc.m010902200
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发表时间：
2001-04-06
影响因子：
4.8
通讯作者：
Koike, A
中科院分区：
文献类型：
--
作者：
Koike, M;Shiomi, T;Koike, A
Ku 是 Ku70 和 Ku80 的异二聚体，在多个核过程中发挥着关键作用，例如DNA 修复、染色体维护和转录调控。异二聚化对于体内 Ku 依赖性 DNA 修复至关重要，尽管其作用尚不清楚。一些证据表明异二聚化对于 Ku70 和 Ku80 的稳定是必需的。在这里，我们表明这些 Ku 亚基的异二聚化对于它们的核进入很重要。当转染到 Ku 缺陷的 xrs-6 细胞中时，带有绿色荧光蛋白标记的外源 Ku70 和 Ku80 积累到细胞核中，而每个核定位信号 (NLS) 功能失调突变体在细胞核中检测不到，这支持了每个 Ku 可以通过其自身的 NLS 易位到细胞核的观点。另一方面，每个 NLS 功能障碍突变体的核积累因外源野生型对应物的存在而显着增强。在表达 Ku 的 HeLa 细胞中，每个 NLS 功能障碍突变体以及野生型 Ku70 和 Ku80 在细胞核中仍然可检测到，而核靶向和二聚化功能均下降的每个 Ku 亚基的双突变体在细胞核中检测不到。我们的结果表明，每个 Ku 亚基不仅可以通过其自身的 NLS，而且还可以通过彼此的异二聚化易位到细胞核。
Ku, a heterodimer of Ku70 and Ku80, plays a key role in multiple nuclear processes, e.g. DNA repair, chromosome maintenance, and transcription regulation. Heterodimerization is essential for Ku-dependent DNA repair in vivo although its role is poorly understood. Some lines of evidence suggest that heterodimerization is required for the stabilization of Ku70 and Ku80. Here we show that the heterodimerization of these Ku subunits is important for their nuclear entry. When transfected into Ku-deficient xrs-6 cells, exogenous Ku70 and Ku80 tagged with green fluorescent protein accumulated into the nucleus, whereas each nuclear localization signal (NLS)-dysfunctional mutant was undetectable in the nucleus, supporting the idea that each Ku can translocate to the nucleus through its own NLS. On the other hand, the nuclear accumulation of each NLS-dysfunctional mutant was markedly enhanced by the presence of an exogenous wild-type counterpart. In Ku-expressing HeLa cells, each NLS-dysfunctional mutant, as well as wild-type Ku70 and Ku80, was still detectable in the nucleus, whereas the double mutant of each Ku subunit with decreased functions of both nuclear targeting and dimerization was undetectable in the nucleus. Our results indicate that each Ku subunit can translocate to the nucleus not only through its own NLS but also through heterodimerization with each other.