Differential mechanisms of LEF/TCF family-dependent transcriptional activation by β-catenin and plakoglobin
Differential mechanisms of LEF/TCF family-dependent transcriptional activation by β-catenin and plakoglobin
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DOI：
10.1128/mcb.20.12.4238-4252.2000
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发表时间：
2000-06-01
影响因子：
5.3
通讯作者：
Ben-Ze'ev, A
中科院分区：
文献类型：
--
作者：
Zhurinsky, J;Shtutman, M;Ben-Ze'ev, A
-连环蛋白和血小板红蛋白是连接钙粘蛋白受体和肌动蛋白细胞骨架的细胞粘附连接的高度同源成分。此外，β - catenin通过在细胞核中与LEF/TCF家族转录因子形成复合物来激活转录。血小板红蛋白也可以与LEF-1结合，当在哺乳动物细胞中过度表达时，可增强LEF-1定向转录。然而，血小板红蛋白过表达导致内源性β -连环蛋白的升高和核易位。我们在这里通过DNA迁移分析表明，与含有β -连环蛋白- lef -DNA的复合物相比，血小板球蛋白- lef /TCF-DNA复合物在体外的形成效率非常低。此外，在血小板转染的细胞中，血小板- lef /TCF-DNA复合物未形成；相反，内源性β -连环蛋白，其水平通过转染血小板红蛋白而升高，形成β -连环蛋白- lef - dna复合物。去除-连环蛋白和血小板蛋白的N端和c端结构域（使犰狳重复结构域完整）诱导血小板蛋白- lef - dna复合物形成，并增强β -连环蛋白- lef - dna复合物的形成，无论是在体外翻译的成分还是在转染的细胞中。转染这些截断的连环蛋白会增加内源性β -连环蛋白的水平，但截断的连环蛋白通过与LEF-1形成转录无活性复合物而成为β -连环蛋白驱动转录的显性阴性抑制剂。当这些连环蛋白突变体通过与连接蛋白跨膜结构域的融合而被阻止进入细胞核时，它们通过增加内源性-连环蛋白水平间接激活转录。这些结果表明，过表达的血小板红蛋白并不直接激活转录，连环蛋白- lef - dna复合物的形成受到连环蛋白N端和c端结构域的负调控。
beta-Catenin and plakoglobin are highly homologous components of cell-cell adherens junctions linking cadherin receptors to the actin cytoskeleton. beta-Catenin, in addition, activates transcription by forming a complex with LEF/TCF family transcription factors in the nucleus. Plakoglobin can also bind to LEF-1 and, when overexpressed in mammalian cells, enhances LEF-1-directed transcription. Plakoglobin overexpression, however, results in the elevation and nuclear translocation of endogenous beta-catenin. We show here, by DNA mobility shift analysis, that the formation of a plakoglobin-LEF/TCF-DNA complex in vitro is very inefficient compared to a complex containing beta-catenin-LEF-DNA. Moreover, in plakoglobin-transfected cells plakoglobin-LEF/TCF-DNA complexes were not formed; rather, the endogenous beta-catenin, whose level is elevated by plakoglobin transfection, formed a beta-catenin-LEF-DNA complex. Removal of the N- and C-terminal domains of both beta-catenin and plakoglobin (leaving the armadillo repeat domain intact) induced plakoglobin-LEF-DNA complex formation and also enhanced beta-catenin-LEF-DNA complexing, both with in vitro-translated components and in transfected cells. Transfection with these truncated catenins increased endogenous beta-catenin levels, but the truncated catenins acted as dominant-negative inhibitors of beta-catenin-driven transcription by forming transcriptionally inactive complexes with LEF-1. When these catenin mutants were prevented from entering the nucleus, by their fusion to the connexin transmembrane domain, they indirectly activated transcription by increasing endogenous beta-catenin levels. These results suggest that overexpression of plakoglobin does not directly activate transcription and that formation of catenin-LEF-DNA complexes is negatively regulated by the catenin N- and C-terminal domains.