DNA Methylation-Dependent Epigenetic Regulation of Gene Expression in MCF-7 Breast Cancer Cells
DNA Methylation-Dependent Epigenetic Regulation of Gene Expression in MCF-7 Breast Cancer Cells
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DOI：
10.4161/epi.1.1.2358
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发表时间：
2006-01-01
期刊：
影响因子：
3.7
通讯作者：
Coleman, William B.
中科院分区：
文献类型：
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作者：
Rivenbark, Ashley G.;Jones, Wendell D.;Coleman, William B.
为了鉴定乳腺癌中的表观遗传调节基因，将MCF-7细胞暴露于250 nM 5-aza或5-aza + 50 nM TSA三周，随后在治疗停止后进行五周恢复期，并通过微阵列分析检查基因表达模式。我们鉴定了20个基因，这些基因在去甲基化处理后表达增加>= 2倍，但在停止处理后恢复到对照水平。RT-PCR证实，所鉴定的基因在对照MCF-7细胞中以低水平或不可检测的水平表达，但在处理的细胞中表达增加。MCF-7细胞中大多数这些推定的表观遗传调控基因不含CpG岛。事实上，这些基因可以基于它们的启动子CpG特征进行分类，包括具有以下特征的基因：（1）典型CpG特征（CpG岛），（2）中间CpG特征（弱CpG岛），和（3）非典型CpG特征（无CpG岛）。来自每个类别的原型基因（包括CpG缺陷基因）被证明是甲基化敏感的（受到CpG甲基化和对去甲基化剂的反应），这表明并非乳腺癌中DNA甲基化的所有基因靶点都包含CpG岛。根据目前的研究结果和文献中的观察，我们建议扩大目前的甲基化依赖性调控基因表达的模型，包括缺乏典型的CpG岛的基因。我们提出的扩展模型认识到，所有的启动子CpG二核苷酸代表DNA甲基化的合法目标，在调控区的关键结构域的特定CpG二核苷酸的甲基化可以导致基因沉默。
To identify epigenetically-regulated genes in breast cancer, MCF-7 cells were exposed to 250 nM 5-aza or 5-aza + 50 nM TSA for three weeks followed by a five week recovery period after treatment withdrawal and gene expression patterns were examined by microarray analysis. We identified 20 genes that are associated with a >= 2-fold increase in expression in response to the demethylating treatment but returned to control levels after treatment withdrawal. RT-PCR verified that the genes identified were expressed at low or undetectable levels in control MCF-7 cells, but increased expression in treated cells. Most of these putative epigentically-regulated genes in MCF-7 cells do not contain CpG islands. In fact, these genes could be classified based upon their promoter CpG features, including genes with: (1) typical CpG features (CpG islands), (2) intermediate CpG features (weak CpG islands), and (3) atypical CpG features (no CpG islands). Prototype genes from each class (including CpG-deficient genes) were shown to be methylation-sensitive (subject to CpG methylation and responsive to demethylating agents), suggesting that not all gene targets of DNA methylation in breast cancer will contain a CpG island. Based upon the results of the current study and observations from the literature, we propose expansion of the current model for methylation-dependent regulation of gene expression to include genes lacking typical CpG islands. The expanded model we propose recognizes that all promoter CpG dinucleotides represent legitimate targets for DNA methylation and that the methylation of specific CpG dinucleotides in critical domains of regulatory regions can result in gene silencing.