Activator protein 2α associates with adenomatous polyposis coli/β-catenin and inhibits β-catenin/T-cell factor transcriptional activity in colorectal cancer cells
Activator protein 2α associates with adenomatous polyposis coli/β-catenin and inhibits β-catenin/T-cell factor transcriptional activity in colorectal cancer cells
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DOI：
10.1074/jbc.m405025200
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发表时间：
2004-10-29
影响因子：
4.8
通讯作者：
Dashwood, RH
中科院分区：
文献类型：
--
作者：
Li, QJ;Dashwood, RH
在大多数人类结直肠癌中，腺瘤性结肠息肉病基因（APC）或CTNNB 1突变组成性激活β-连环蛋白/T细胞因子（TCF）/淋巴增强因子（LEF）信号通路。在这里，我们表明，转录因子激活蛋白（AP）-2 α抑制β-连环蛋白/TCF-响应报告在人胚肾293细胞和两个人结直肠癌细胞系，尽管事实上，β-连环蛋白和TCF-4蛋白水平在细胞核中是不变的。免疫共沉淀研究表明，AP-2 α与APC和β-连环蛋白形成复合物，AP-2 α破坏了细胞核中β-连环蛋白/TCF-4的相互作用。因此，AP-2 α APC β-连环蛋白复合物的形成似乎通过使核β-连环蛋白库向无活性形式移动而抑制β-连环蛋白反式激活，从而降低了与TCF/LEF转录因子的结合。Glucose-转移酶下拉分析表明，AP-2 α与APC而不是β-连环蛋白物理相关，AP-2 α结合位点位于APC的N末端，涉及七肽和犰狳重复结构域，而AP-2 α中的APC结合位点位于C末端DNA结合结构域的碱性区域。这些发现为肿瘤抑制蛋白APC和转录因子AP-2 α之间的特异性相互作用提供了第一个证据，并且它们表明Wnt信号通路和与AP-2 α相关的各种其他发育和分化通路之间存在联系。
In most human colorectal cancers, mutations in the adenomatous polyposis coli gene (APC) or CTNNB1 constitutively activate the beta-catenin/T-cell factor (TCF)/lymphoid enhancer factor (LEF) signaling pathway. Here, we show that the transcription factor activator protein (AP)-2alpha inhibited a beta-catenin/TCF-responsive reporter in human embryonic kidney 293 cells and in two human colorectal cancer lines, despite the fact that beta-catenin and TCF-4 protein levels were unchanged in the nucleus. Co-immunoprecipitation studies revealed that AP-2alpha formed a complex with APC and beta-catenin and that AP-2alpha disrupted beta-catenin/TCF-4 interactions in the nucleus. Thus, AP-2alpha.APC.beta-catenin complex formation appears to suppress beta-catenin transactivation by shifting the pool of nuclear beta-catenin toward an inactive form, having reduced binding to TCF/LEF transcription factors. Glutathione S-transferase pull-down assays showed that AP-2alpha physically associated with APC rather than with beta-catenin, and the AP-2alpha binding site was identified in the N terminus of APC, involving both the heptad and armadillo repeat domains, whereas the APC binding site in AP-2alpha was in the basic region of the C-terminal DNA binding domain. These findings provide the first evidence for a specific interaction between the tumor suppressor protein APC and the transcription factor AP-2alpha, and they suggest a link between the Wnt signaling pathway and various other pathways of development and differentiation associated with AP-2alpha.