Dinucleotide repeats negatively modulate the promoter activity of Cyr61 and is unstable in hepatocellular carcinoma patients
Dinucleotide repeats negatively modulate the promoter activity of Cyr61 and is unstable in hepatocellular carcinoma patients
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DOI：
10.1038/sj.onc.1208550
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发表时间：
2005-06-02
期刊：
影响因子：
8
通讯作者：
Lee, CGL
中科院分区：
文献类型：
--
作者：
Wang, BS;Ren, JW;Lee, CGL
Cyr61 是一种分泌型、富含半胱氨酸的肝素结合蛋白，介导多种功能，包括细胞外基质形成、分化、细胞增殖、粘附、迁移、存活以及血管生成和肿瘤发生。在这项研究中，我们发现肝细胞癌（HCC）患者的肿瘤中Cyr61基因表达显着下调。为了阐明其基因调控机制，我们检查了 Cyr61 的启动子。它包含两个长重复序列，每个重复序列包含 HNF3 β 和 ATF 结合位点下游的 d(CA) 二核苷酸重复序列。我们假设 d(CA) 重复序列可能在调节 Cyr61 启动子活性中发挥重要作用，并进行了启动子报告基因检测来检验这一点。我们发现，在 KB3-1 和 HepG2 细胞系中，更多数量的 d(CA) 重复会导致 Cyr61 基因的启动子活性显着降低，但在 MCF-7 细胞系中则不然。此外，发现 d(CA) 重复序列（而非其他随机序列）对 Cyr61 启动子活性很重要。我们进一步证明 d(CA) 重复上游的 ATF 和 HNF3 β 结合位点分别正向和负向调节 Cyr61 启动子活性。对 HCC 患者 Cyr61 启动子中 d(CA) 二核苷酸模式的检查显示，大约 32% 的患者在肿瘤、邻近正常肝组织或两者中表现出杂合性丢失或体细胞嵌合。
Cyr61 is a secreted, cysteine-rich, heparin-binding protein that mediates diverse functions including extracellular matrix formation, differentiation, cell proliferation, adhesion, migration, survival, as well as angiogenesis and tumorigenesis. In this study, we found that Cyr61 gene expression is significantly downregulated in the tumors of hepatocellular carcinoma (HCC) patients. To elucidate its mechanism of gene regulation, we examined the promoter of Cyr61. which contains two long stretches of repeats, each comprising d(CA) dinucleotide repeats downstream of HNF3 beta- and ATF-binding sites. We hypothesized that the d(CA) repeats may play an important role in regulating Cyr61 promoter activity and performed promoter reporter assays to examine this. We found that a greater number of d(CA) repeats resulted in significantly lower promoter activity of the Cyr61 gene in the KB3-1 and HepG2 cell lines, but not in the MCF-7 cell line. In addition, the d(CA) repeats, but not other random sequences, were found to be important for Cyr61 promoter activity. We further demonstrate that the ATF- and HNF3 beta-binding sites upstream the d(CA) repeats positively and negatively modulate Cyr61 promoter activity, respectively. An examination of the d(CA) dinucleotide patterns in the Cyr61 promoter in HCC patients revealed that similar to 32% of these patients exhibited either loss of heterozygosity or somatic mosaicism in either the tumors, adjacent normal liver tissues or both.