Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
Clin Exp Metastasis. 2011 Apr;28(4):391-404. doi: 10.1007/s10585-011-9378-8. Epub 2011 Feb 20.
As a member of adherens junction, p120-catenin (p120ctn) plays a major role in cell adhesions through stabilization of E-cadherin. p120ctn is transcriptionally down-regulated in non-small cell lung cancer (NSCLC), although the molecular mechanisms underlying p120ctn repression are incompletely defined. Here we further investigated transcriptional regulation of p120ctn in NSCLC. We prepared a promoter reporter plasmid construct that contained p120ctn promoter region from position -1082 to +320 relative to transcription start site. Through serial deletion mutation analysis of the p120ctn promoter, we pinpointed cis-acting elements involved in regulation of p120ctn. We identified transcription factor SP1 as a transcriptional repressor of p120ctn that directly binds to segment (-9 to +36) of the p120ctn promoter. SP1 can receive multiple signals from several intracellular signaling pathways. Through examination of SP1 binding partners, we identified proto-oncogene c-Crk to be involved in transcriptional down-regulation of p120ctn. RNAi mediated silencing of CRK in A549, H157 and H358 cells increased p120ctn protein levels. On the other hand, over-expression of CRK-I and CRK-II in NSCLC cells down-regulated p120ctn, an effect that was abrogated by simultaneous silencing of SP1. In summary, our data provide evidence for the role of c-Crk proto-oncogene in transcriptional repression of p120ctn that further clarifies the mechanism by which this biochemical signal promotes metastasis in NSCLC.
作为黏着连接的一个组成部分，p120 连环蛋白（p120ctn）通过稳定 E-钙黏蛋白在细胞黏附中发挥主要作用。尽管 p120ctn 抑制的分子机制尚未完全明确，但 p120ctn 在非小细胞肺癌（NSCLC）中呈转录下调。在此，我们进一步研究了 NSCLC 中 p120ctn 的转录调控。我们制备了一个启动子报告质粒构建体，其中包含转录起始位点前 -1082 至 +320 位置的 p120ctn 启动子区域。通过对 p120ctn 启动子的串联缺失突变分析，我们确定了参与 p120ctn 调控的顺式作用元件。我们确定转录因子 SP1 是 p120ctn 的转录抑制剂，它直接结合 p120ctn 启动子的 (-9 至 +36) 片段。SP1 可以从几个细胞内信号通路接收多个信号。通过检查 SP1 结合伙伴，我们发现原癌基因 c-Crk 参与了 p120ctn 的转录下调。在 A549、H157 和 H358 细胞中，通过 RNAi 介导的 CRK 沉默增加了 p120ctn 蛋白水平。另一方面，在 NSCLC 细胞中过表达 CRK-I 和 CRK-II 会下调 p120ctn，而同时沉默 SP1 则可以消除这种下调作用。总之，我们的数据为 c-Crk 原癌基因在 p120ctn 转录抑制中的作用提供了证据，进一步阐明了这种生化信号促进 NSCLC 转移的机制。
