NLS-dependent nuclear localization of p120ctn is necessary to relieve Kaiso-mediated transcriptional repression
NLS-dependent nuclear localization of p120ctn is necessary to relieve Kaiso-mediated transcriptional repression
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DOI：
10.1242/jcs.01101
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发表时间：
2004-06-01
影响因子：
4
通讯作者：
Daniel, JM
中科院分区：
文献类型：
--
作者：
Kelly, KF;Spring, CM;Daniel, JM
犰狳连环蛋白 p120(ctn) 调节质膜上的钙粘蛋白粘附强度，并与细胞核中新型 BTB/POZ 转录抑制因子 Kaiso 相互作用。 p120(ctn) 在细胞-细胞连接处和细胞核中的双重定位表明其核细胞质运输受到严格调控。在此，我们报告了 p120(ctn) 中特异性且高度碱性的核定位信号 (NLS) 的鉴定。 NLS 的功能通过其指导异源 β-半乳糖苷酶-GFP 融合蛋白的核定位的能力得到验证。将全长 p120(ctn) 的 NLS 中两个关键的带正电荷的赖氨酸突变为中性丙氨酸，可抑制 p120(ctn) 核定位以及与细胞迁移增加相关的特征性 p120(ctn) 诱导的分支表型。然而，虽然这些发现和其他发现表明 p120(ctn) 的核定位对于 p120ctn 诱导的分支表型至关重要，但我们发现野生型和 NLS 突变的 p120(ctn) 的强制核定位不会诱导分支。最近，我们还发现p120(ctn)的作用之一是调节Kaiso介导的转录抑制。然而，目前尚不清楚p120(ctn)是否将Kaiso隔离在细胞质中或直接抑制细胞核中的Kaiso转录活性。使用最小启动子测定，我们在此表明 p120(ctn) 对 Kaiso 转录活性的调节作用需要 p120(ctn) 的核转位。因此，p120(ctn) 中完整的 NLS 是其首次确定转录抑制子 Kaiso 的调节作用所必需的。
The Armadillo catenin p120(ctn) regulates cadherin adhesive strength at the plasma membrane and interacts with the novel BTB/POZ transcriptional repressor Kaiso in the nucleus. The dual localization of p120(ctn) at cell-cell junctions and in the nucleus suggests that its nucleocytoplasmic trafficking is tightly regulated. Here we report on the identification of a specific and highly basic nuclear localization signal (NLS) in p120(ctn). The functionality of the NLS was validated by its ability to direct the nuclear localization of a heterologous beta-galactosidase-GFP fusion protein. Mutating two key positively charged lysines to neutral alanines in the NLS of full-length p120(ctn) inhibited both p120(ctn) nuclear localization as well as the characteristic p120(ctn)-induced branching phenotype that correlates with increased cell migration. However, while these findings and others suggested that nuclear localization of p120(ctn) was crucial for the p120ctn-induced branching phenotype, we found that forced nuclear localization of both wild-type and NLS-mutated p120(ctn) did not induce branching. Recently, we also found that one role of p120(ctn) was to regulate Kaiso-mediated transcriptional repression. However, it remained unclear whether p120(ctn) sequestered Kaiso in the cytosol or directly inhibited Kaiso transcriptional activity in the nucleus. Using minimal promoter assays, we show here that the regulatory effect of p120(ctn) on Kaiso transcriptional activity requires the nuclear translocation of p120(ctn). Therefore, an intact NLS in p120(ctn) is requisite for its first identified regulatory role of the transcriptional repressor Kaiso.