c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells.
c-Myc activates BRCA1 gene expression through distal promoter elements in breast cancer cells.
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DOI：
10.1186/1471-2407-11-246
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发表时间：
2011-06-13
期刊：
影响因子：
3.8
通讯作者：
Olopade OI
中科院分区：
文献类型：
--
作者：
Chen Y;Xu J;Borowicz S;Collins C;Huo D;Olopade OI
BRCA1基因在维持基因组稳定性方面起着重要作用。BRCA1失活与乳腺癌的发生有关。越来越多的转录因子被证明调节BRCA1的表达。C-Myc可以作为转录激活剂，调节人类基因组中高达15%的基因，高通量筛选的结果表明BRCA1是它的靶标之一。在这篇报道中，我们使用培养的乳腺癌细胞来研究c-Myc在转录水平激活BRCA1的机制。在培养的乳腺癌细胞中，c-Myc通过c-Myc特异的siRNAs被耗尽。定量RT-PCR检测BRCA1基因表达，Western印迹检测BRCA1蛋白表达，并在此条件下检测BRCA1启动子活性。进行DNA序列分析，寻找与BRCA1启动子区域E盒高度相似的区域。用染色质免疫沉淀法检测c-Myc与BRCA1启动子在体内的相关性。我们通过在假定的E盒中进行核苷酸替换的启动子分析，研究了BRCA1启动子区域c-Myc结合位点的功能。用GFP-Report法检测BRCA1依赖的DNA修复活性。C-Myc的缺失与BRCA1mRNA和BRCA1蛋白的表达水平降低有关。C-Myc的缺失降低了BRCA1启动子的活性，而异位表达的c-Myc增加了BRCA1的启动子活性。在BRCA1启动子的远端，DNA序列分析显示有两个高度相似的串联簇，每个簇包含一个可能的c-Myc结合位点。C-Myc在体内与这些区域结合。这些区域c-Myc结合位点的核苷酸替换取消了c-Myc依赖的启动子的激活。此外，由于c-Myc缺失而导致BRCA1表达降低的乳腺癌细胞表现出DNA修复活性受损。BRCA1远端启动子区域与c-Myc相关，参与BRCA1基因的激活。
The BRCA1 gene plays an important role in the maintenance of genomic stability. BRCA1 inactivation contributes to breast cancer tumorigenesis. An increasing number of transcription factors have been shown to regulate BRCA1 expression. c-Myc can act as a transcriptional activator, regulating up to 15% of all genes in the human genome and results from a high throughput screen suggest that BRCA1 is one of its targets. In this report, we used cultured breast cancer cells to examine the mechanisms of transcriptional activation of BRCA1 by c-Myc. c-Myc was depleted using c-Myc-specific siRNAs in cultured breast cancer cells. BRCA1 mRNA expression and BRCA1 protein expression were determined by quantitative RT-PCR and western blot, respectively and BRCA1 promoter activities were examined under these conditions. DNA sequence analysis was conducted to search for high similarity to E boxes in the BRCA1 promoter region. The association of c-Myc with the BRCA1 promoter in vivo was tested by a chromatin immunoprecipitation assay. We investigated the function of the c-Myc binding site in the BRCA1 promoter region by a promoter assay with nucleotide substitutions in the putative E boxes. BRCA1-dependent DNA repair activities were measured by a GFP-reporter assay. Depletion of c-Myc was found to be correlated with reduced expression levels of BRCA1 mRNA and BRCA1 protein. Depletion of c-Myc decreased BRCA1 promoter activity, while ectopically expressed c-Myc increased BRCA1 promoter activity. In the distal BRCA1 promoter, DNA sequence analysis revealed two tandem clusters with high similarity, and each cluster contained a possible c-Myc binding site. c-Myc bound to these regions in vivo. Nucleotide substitutions in the c-Myc binding sites in these regions abrogated c-Myc-dependent promoter activation. Furthermore, breast cancer cells with reduced BRCA1 expression due to depletion of c-Myc exhibited impaired DNA repair activity. The distal BRCA1 promoter region is associated with c-Myc and contributes to BRCA1 gene activation.
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影响因子：
56.9
作者：
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通讯作者：
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