Song Jing, Du Zhanwen, Ravasz Mate, Dong Bohan, Wang Zhenghe, Ewing Rob M
Center for Proteomics and Bioinformatics, Case Western Reserve University, Cleveland, Ohio.
Department of Genetics and Genome Science, Case Western Reserve University, Cleveland, Ohio.
Mol Cancer Res. 2015 Jun;13(6):969-81. doi: 10.1158/1541-7786.MCR-13-0644. Epub 2015 Mar 9.
Aberrant activation of the Wnt signaling pathway is an important step in the initiation and progression of tumor development in diverse cancers. The central effector of canonical Wnt signaling, β-catenin (CTNNB1), is a multifunctional protein, and has been extensively studied with respect to its roles in cell-cell adhesion and in regulation of Wnt-driven transcription. Here, a novel mass spectrometry-based proteomics technique in colorectal cancer cells expressing stabilized β-catenin, was used to identify a protein-protein interaction between β-catenin and DNA methyltransferase I (Dnmt1) protein, the primary regulator of DNA methylation patterns in mammalian cells. Dnmt1 and β-catenin strongly colocalized in the nuclei of colorectal cancer cells, and the interaction is mediated by the central domain of the Dnmt1 protein. Dnmt1 protein abundance is dependent upon the levels of β-catenin, and is increased in cells expressing stabilized mutant β-catenin. Conversely, the Dnmt1 regulates the levels of nuclear β-catenin and β-catenin/TCF-driven transcription. In addition, lysine-specific demethylase 1 (LSD1/KDM1A), a regulator of DNMT1 stability, was identified as a component of the Dnmt1-β-catenin protein complex and perturbation of the Dnmt1-β-catenin interaction altered DNA methylation. In summary, a functional protein-protein interaction was identified between two critically important oncoproteins, in turn revealing a link between Wnt signaling and downstream nuclear functions mediated by Dnmt1.
Two critical oncoproteins, Dnmt1 and β-catenin, mutually regulate one each other's levels and activities in colorectal cancer cells.
Wnt信号通路的异常激活是多种癌症肿瘤发生和发展的重要步骤。经典Wnt信号通路的核心效应分子β-连环蛋白（CTNNB1）是一种多功能蛋白，其在细胞间黏附以及Wnt驱动的转录调控中的作用已得到广泛研究。在此，一种基于质谱的新型蛋白质组学技术被用于在表达稳定化β-连环蛋白的结肠癌细胞中，鉴定β-连环蛋白与DNA甲基转移酶I（Dnmt1）蛋白之间的蛋白质-蛋白质相互作用，Dnmt1是哺乳动物细胞中DNA甲基化模式的主要调节因子。Dnmt1和β-连环蛋白在结肠癌细胞核中强烈共定位，且这种相互作用由Dnmt1蛋白的中央结构域介导。Dnmt1蛋白丰度取决于β-连环蛋白的水平，并在表达稳定化突变型β-连环蛋白的细胞中增加。相反，Dnmt1调节核β-连环蛋白水平以及β-连环蛋白/TCF驱动的转录。此外，赖氨酸特异性去甲基化酶1（LSD1/KDM1A），一种DNMT1稳定性的调节因子，被鉴定为Dnmt1-β-连环蛋白蛋白复合物的一个组成部分，并且Dnmt1-β-连环蛋白相互作用的扰动改变了DNA甲基化。总之，在两种至关重要的癌蛋白之间鉴定出了一种功能性蛋白质-蛋白质相互作用，进而揭示了Wnt信号与由Dnmt1介导的下游核功能之间的联系。
两种关键癌蛋白Dnmt1和β-连环蛋白在结肠癌细胞中相互调节彼此的水平和活性。
