Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), TRUE Campus, CN-6, Sector-V, Salt Lake, Kolkata- 700091 & 4, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India.
Cancer Biology and Inflammatory Disorder Division, Council of Scientific and Industrial Research-Indian Institute of Chemical Biology (CSIR-IICB), TRUE Campus, CN-6, Sector-V, Salt Lake, Kolkata- 700091 & 4, Raja S.C. Mullick Road, Jadavpur, Kolkata 700032, India.
Biochim Biophys Acta Mol Cell Res. 2022 Mar;1869(3):119185. doi: 10.1016/j.bbamcr.2021.119185. Epub 2021 Dec 7.
Emerging evidences suggest abundant expression of Carboxy terminus of Hsc70 Interacting Protein or CHIP (alias STIP1 Homology and U-box Containing Protein 1 or STUB1) in colorectal carcinoma, but the mechanistic detail of this augmented expression pattern is unclear. The signature driver of canonical Wnt pathway, β-catenin, and its co-activator RNA helicase p68, are also overexpressed in colorectal carcinoma. In this study, we describe a novel mechanism of Wnt/β-catenin and p68 mediated transcriptional activation of CHIP gene leading to enhanced proliferation of colorectal carcinoma cells. Bioinformatic analyses reconfirmed an elevated CHIP expression level in colorectal carcinoma datasets. Wnt3A treatment and pharmacological activation of canonical Wnt signaling pathway resulted in increased nuclear translocation of β-catenin, augmenting CHIP expression. Likewise, immunoblotting and Real time PCR following overexpression and knockdown of β-catenin and p68 demonstrated upregulated and downregulated CHIP expression, respectively, at both mRNA and protein levels. p68 along with β-catenin were found to occupy Transcription Factor 4 (TCF4) binding sites on endogenous CHIP promoter and regulate its transcription. After cloning CHIP promoter, the increased and decreased promoter activities of CHIP induced by overexpression and knockdown of either β-catenin or p68 further confirmed transcriptional regulation of CHIP gene by Wnt/β-catenin signaling cascade. Finally, enhanced cellular propagation and migration of colorectal carcinoma cells induced by 'Wnt/β-catenin-p68-CHIP' axis established the significance of this pathway in oncogenesis. To the best of our knowledge, this is the first report elucidating the mechanistic details of transcriptional regulation of CHIP (STUB1) gene expression.
越来越多的证据表明羧基末端热休克蛋白 70 相互作用蛋白（CHIP）或 STIP1 同源物和 U -box 含有蛋白 1（STUB1）在结直肠癌中大量表达，但这种增强表达模式的机制细节尚不清楚。经典 Wnt 途径的标志性驱动子β-连环蛋白及其共激活 RNA 解旋酶 p68 也在结直肠癌中过表达。在这项研究中，我们描述了一种新的机制，即 Wnt/β-连环蛋白和 p68 介导 CHIP 基因的转录激活，导致结直肠癌细胞增殖增强。生物信息学分析再次证实了结直肠癌数据集中 CHIP 表达水平升高。Wnt3A 处理和经典 Wnt 信号通路的药理学激活导致 β-连环蛋白核易位增加，从而增强 CHIP 表达。同样，β-连环蛋白和 p68 的过表达和敲低后进行免疫印迹和实时 PCR 分析，分别显示 CHIP 在 mRNA 和蛋白质水平上的表达上调和下调。发现 p68 与 β-连环蛋白一起占据内源性 CHIP 启动子上的转录因子 4（TCF4）结合位点，并调节其转录。克隆 CHIP 启动子后，过表达和敲低β-连环蛋白或 p68 分别诱导的 CHIP 启动子活性增加和减少进一步证实了 Wnt/β-连环蛋白信号级联对 CHIP 基因的转录调节。最后，由“Wnt/β-连环蛋白-p68-CHIP”轴诱导的结直肠癌细胞的增强细胞增殖和迁移确立了该途径在肿瘤发生中的重要性。据我们所知，这是首次阐明 CHIP（STUB1）基因表达转录调节的机制细节的报告。
