Promoter methylation inhibits BRD7 expression in human nasopharyngeal carcinoma cells.
Promoter methylation inhibits BRD7 expression in human nasopharyngeal carcinoma cells.
复制标题
启动子甲基化抑制人鼻咽癌细胞中 BRD7 的表达。
DOI：
10.1186/1471-2407-8-253
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发表时间：
2008-09-08
期刊：
影响因子：
3.8
通讯作者：
Li G
中科院分区：
文献类型：
--
作者：
Liu H;Zhang L;Niu Z;Zhou M;Peng C;Li X;Deng T;Shi L;Tan Y;Li G
鼻咽癌是一种高发于东南亚和中国南部的头颈部恶性肿瘤。最近的研究结果表明，多个抑癌基因的表观遗传失活在鼻咽癌的发生发展中起重要作用。BRD7是一种与鼻咽癌相关的溴域基因，其在正常鼻咽癌组织和细胞系中的表达水平明显高于鼻咽癌活检组织和细胞系。在本研究中，我们探讨了DNA甲基化在BRD7转录调控中的作用。EMBOSS CpGlot和Softberry CpGFinder分别预测了BRD7启动子中CpG岛的存在。采用巢式甲基化特异性聚合酶链式反应和逆转录聚合酶链式反应检测肿瘤细胞株和临床标本中BRD7启动子的甲基化状态和BRD7基因的表达。用凝胶迁移率改变分析(EMSA)和荧光素酶分析检测胞嘧啶甲基化对核蛋白与BRD7启动子结合的影响。我们发现DNA甲基化抑制了鼻咽癌细胞中BRD7的表达。在体外，鼻咽癌细胞中的DNA甲基化抑制了BRD7启动子的活性，并抑制了核蛋白(可能是Sp1)与BRD7启动子中的Sp1结合位点的结合。相反，抑制DNA甲基化增加了鼻咽癌细胞内源性BRD7mRNA的诱导。我们还发现，在鼻咽癌患者和配对的鼻咽癌患者血液样本中，BRD7启动子甲基化频率明显高于正常人血液样本。BRD7启动子去甲基化是高水平诱导BRD7基因表达的前提。BRD7启动子DNA甲基化可作为鼻咽癌的诊断指标。
Nasopharyngeal carcinoma (NPC) is a head and neck malignancy with high occurrence in South-East Asia and Southern China. Recent findings suggest that epigenetic inactivation of multiple tumor suppressor genes plays an important role in the tumourigenesis of NPC. BRD7 is a NPC-associated bromodomain gene that exhibits a much higher-level of mRNA expression in normal than in NPC biopsies and cell lines. In this study, we explored the role of DNA methylation in regulation of BRD7 transcription. The presence of CpG islands within BRD7 promoter was predicted by EMBOSS CpGplot and Softberry CpGFinder, respectively. Nested methylation-specific PCR and RT-PCR were employed to detect the methylation status of BRD7 promoter and the mRNA expression of BRD7 gene in tumor cell lines as well as clinical samples. Electrophoretic mobility shift assays (EMSA) and luciferase assay were used to detect the effects of cytosine methylation on the nuclear protein binding to BRD7 promoter. We found that DNA methylation suppresses BRD7 expression in NPC cells. In vitro DNA methylation in NPC cells silenced BRD7 promoter activity and inhibited the binding of the nuclear protein (possibly Sp1) to Sp1 binding sites in the BRD7 promoter. In contrast, inhibition of DNA methylation augments induction of endogenous BRD7 mRNA in NPC cells. We also found that methylation frequency of BRD7 promoter is much higher in the tumor and matched blood samples from NPC patients than in the blood samples from normal individuals. BRD7 promoter demethylation is a prerequisite for high level induction of BRD7 gene expression. DNA methylation of BRD7 promoter might serve as a diagnostic marker in NPC.
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