Molecular mechanism of transcriptional repression of gelsolin in human breast cancer cells
Molecular mechanism of transcriptional repression of gelsolin in human breast cancer cells
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DOI：
10.1006/excr.2002.5534
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发表时间：
2002-06-10
影响因子：
3.7
通讯作者：
Asch, BB
中科院分区：
文献类型：
--
作者：
Dong, Y;Asch, HL;Asch, BB
凝溶胶蛋白（一种肿瘤抑制因子）的缺失是多种病因的乳腺癌中最常见的分子缺陷之一，并且至少存在于三种动物物种中：人、小鼠和大鼠。我们之前对乳腺癌细胞的分析表明，这种缺陷不是由于凝溶胶蛋白基因突变，而是由于表观遗传因素，包括基因转录减少。本文所述的研究提供了人凝溶胶蛋白启动子的第一个功能表征，并揭示了减少凝溶胶蛋白转录的机制基础。在报告基因测定中，凝溶胶蛋白启动子在低凝溶胶蛋白表达的乳腺癌细胞中活性较低。一个顺式元件介导的这种降低的启动子活性被定义为一个27 bp的序列位于约135 bp的转录起始位点上游。凝胶位移和超位移分析以及Southwestern印迹分析表明，转录激活因子-1（ATF-1）和一个分子量约为100 kDa的蛋白质可能具有与27 bp凝溶胶蛋白顺式元件结合的癌细胞特异性DNA结合活性。虽然ATF-1蛋白在良性和致瘤性乳腺细胞中高度表达，但其DNA结合活性在癌细胞中选择性丰富，并与凝溶胶蛋白mRNA水平呈负相关。因此，我们的研究结果表明，ATF-1在凝溶胶蛋白启动子沉默中的作用与其对各种其他启动子的反式激活作用相反。(C)2002 Elsevier Science（美国）。
Loss of gelsolin, a tumor suppressor, is one of the most frequently occurring molecular defects, in breast cancers of diverse etiologies and across at least three animal species: human, mouse, and rat. Our previous analysis of breast cancer cells demonstrated that the deficiency is not due to mutation of the gelsolin gene, but instead to epigenetic factors, including decreased transcription of the gene. The study described herein provides the first functional characterization of the human gelsolin promoter and reveals a mechanistic basis for the reduced gelsolin transcription. In reporter gene assays, the gelsolin promoter was less active in low-gelsolin-expressing breast cancer cells. A cis-element mediating this reduced promoter activity was defined as a 27-bp sequence located approximately 135 bp upstream of the transcription start site. Gel shift and supershift assays and Southwestern blotting analysis indicated that activating transcription factor-1 (ATF-1) and a protein of similar to100 kDa may have cancer cell-specific DNA-binding activity to the 27-bp gelsolin cis-element. Although the ATF-1 protein was highly expressed in both benign and tumorigenic breast cells, its DNA-binding activity was selectively abundant in the cancer cells and correlated inversely with the gelsolin mRNA level. Thus, our results suggest a role for ATF-1 in gelsolin promoter silencing in contrast to its transactivating effect on various other promoters. (C) 2002 Elsevier Science (USA).