Wnt/β-Catenin Signaling Regulates Yes-associated Protein (YAP) Gene Expression in Colorectal Carcinoma Cells
Wnt/β-Catenin Signaling Regulates Yes-associated Protein (YAP) Gene Expression in Colorectal Carcinoma Cells
复制标题
DOI：
10.1074/jbc.m111.327767
复制
发表时间：
2012-04-06
影响因子：
4.8
通讯作者：
Yochum, Gregory S.
中科院分区：
文献类型：
--
作者：
Konsavage, Wesley M., Jr.;Kyler, Sydney L.;Yochum, Gregory S.
Wnt/β -连环蛋白通路的突变发生在大多数结直肠癌（CRC）中，这些突变导致β -连环蛋白转录共激活因子在细胞核内的积累增加。在细胞核中，β -连环蛋白与TCF/LEF序列特异性转录因子结合，激活靶基因表达。Hippo通路通过阻止Yes相关蛋白（YAP）转录共激活因子在细胞核内的积累来限制细胞生长。YAP在CRC中的表达升高，这表明，与Wnt/β -连环蛋白信号通路一样，Hippo通路可能有助于结直肠癌的发生。YAP在翻译后水平的调控已得到充分研究，但控制YAP基因表达的转录因子尚不清楚。在此我们证明，β -连环蛋白/TCF4复合物结合YAP基因第一个内含子内的一个DNA增强子元件，以驱动CRC细胞中YAP的表达。因此，使用shRNAs降低CRC细胞中β -连环蛋白的表达会导致YAP的mRNA和蛋白质水平下降。YAP在几种已建立的人结肠癌细胞系的细胞质和细胞核中大量表达，并且这种定位模式对铺板密度不敏感。最后，我们表明，与未受累的结肠黏膜中的表达相比，在一组原发性人结直肠肿瘤的大多数中YAP表达升高，并且YAP和β -连环蛋白定位于肿瘤细胞的核区室。总之，这些结果表明YAP是一种癌基因，其表达由人CRC细胞中异常的Wnt/β -连环蛋白信号驱动。
Mutations in the Wnt/beta-catenin pathway occur in most colorectal cancers (CRCs), and these mutations lead to increased nuclear accumulation of the beta-catenin transcriptional co-activator. In the nucleus, beta-catenin associates with TCF/LEF sequence specific transcription factors to activate target gene expression. The Hippo pathway restricts cellular growth by preventing nuclear accumulation of the Yes-associated protein (YAP) transcriptional co-activator. YAP expression is elevated in CRCs suggesting that, like Wnt/beta-catenin signaling, the Hippo pathway may contribute to colorectal carcinogenesis. Regulation of YAP at the post-translational level has been well studied but the transcription factors that control YAP gene expression are unknown. Here we demonstrate that beta-catenin/TCF4 complexes bind a DNA enhancer element within the first intron of the YAP gene to drive YAP expression in CRC cells. As such, reducing beta-catenin expression in CRC cells using shRNAs leads to decreased YAP mRNA and protein levels. YAP is abundantly expressed in the cytoplasm and nuclei of several established human colon cancer cell lines and this localization pattern is insensitive to plating density. Finally, we show that YAP expression is elevated in the majority of a panel of primary human colorectal tumors compared with its expression in uninvolved colonic mucosa, and that YAP and beta-catenin localize to the nuclear compartment of tumor cells. Together, these results implicate YAP as an oncogene whose expression is driven by aberrant Wnt/beta-catenin signaling in human CRC cells.