Department of Gastroenterology and Hepatology, Hokkaido University Graduate School of Medicine, Sapporo, Japan.
PLoS One. 2013 Jun 20;8(6):e66255. doi: 10.1371/journal.pone.0066255. Print 2013.
CD133 is a cellular surface protein that has been reported to be a cancer stem cell marker, and thus it is considered to be a potential target for cancer treatment. However, the mechanism regulating CD133 expression is not yet understood. In this study, we analyzed the activity of five putative promoters (P1-P5) of CD133 in human embryonic kidney (HEK) 293 cells and colon cancer cell line WiDr, and found that the activity of promoters, particularly of P5, is elevated by overexpression of hypoxia-inducible factors (HIF-1α and HIF-2α). Deletion and mutation analysis identified one of the two E-twenty six (ETS) binding sites (EBSs) in the P5 region as being essential for its promoter activity induced by HIF-1α and HIF-2α. In addition, a chromatin imunoprecipitation assay demonstrated that HIF-1α and HIF-2α bind to the proximal P5 promoter at the EBSs. The immunoprecipitation assay showed that HIF-1α physically interacts with Elk1; however, HIF-2α did not bind to Elk1 or ETS1. Furthermore, knockdown of both HIF-1α and HIF-2α resulted in a reduction of CD133 expression in WiDr. Taken together, our results revealed that HIF-1α and HIF-2α activate CD133 promoter through ETS proteins.
CD133 是一种细胞表面蛋白，据报道它是癌症干细胞标志物，因此被认为是癌症治疗的潜在靶点。然而，调节 CD133 表达的机制尚不清楚。在这项研究中，我们分析了 CD133 的五个假定启动子（P1-P5）在人胚肾（HEK）293 细胞和结肠癌 WiDr 细胞系中的活性，发现启动子的活性，特别是 P5 的活性，通过缺氧诱导因子（HIF-1α 和 HIF-2α）的过表达而升高。缺失和突变分析确定了 P5 区域中的两个 E 盒结合位点（EBS）之一对于 HIF-1α 和 HIF-2α 诱导的启动子活性是必需的。此外，染色质免疫沉淀分析表明，HIF-1α 和 HIF-2α 在 EBS 处结合到近端 P5 启动子。免疫沉淀分析表明，HIF-1α 与 Elk1 发生物理相互作用；然而，HIF-2α 不与 Elk1 或 ETS1 结合。此外，敲低 HIF-1α 和 HIF-2α 均可导致 WiDr 中 CD133 表达减少。总之，我们的结果表明，HIF-1α 和 HIF-2α 通过 ETS 蛋白激活 CD133 启动子。
