ERegulation of the estrogen receptor a minimal promoter by Sp1, USF-1 and ERa
ERegulation of the estrogen receptor a minimal promoter by Sp1, USF-1 and ERa
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DOI：
10.1023/b:brea.0000025398.93829.78
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发表时间：
2004-05-01
影响因子：
3.8
通讯作者：
Fuqua, SAW
中科院分区：
文献类型：
--
作者：
deGraffenried, LA;Hopp, TA;Fuqua, SAW
调控雌激素受体α(ERpha)在乳腺肿瘤中表达的确切分子机制尚不清楚，但研究表明，它们部分处于转录水平。我们专注于调节ERpha最小启动子的转录因子，我们之前已经证明它位于基因5‘侧翼区的前245个核苷酸内。在这个区域内有几个元件对于ERpha启动子的完整转录活性是必不可少的，包括一个GC盒和一个不完善的E盒。在早期的研究中，我们证明了Sp1转录因子家族在调节ERpha表达中的重要功能。我们现在已经确定USF-1和ERAlpha本身都是转录因子多蛋白复合体的组成部分，该复合体在ERAlpha最小启动子上相互作用，对其完整的转录活性是必不可少的。电泳迁移率改变分析表明，Sp1和USF-1，而不是ERpha，直接与ERpha最小启动子结合。我们通过GST下拉试验表明，Era在体外能够与USF-1相互作用，这表明除了Era和Sp1之间可能的相互作用外，ERpha还能够与蛋白质复合体相互作用。在MCF-7乳腺癌细胞中联合外源表达该复合体的各组分，对ERAlpha最小启动子的反式激活有协同作用，提示该蛋白质复合体的重要性在于各组分之间的相互作用。基于这些发现，我们提出了一种可能的ERAlpha最小启动子转录模型。
The exact molecular mechanisms regulating estrogen receptor alpha (ERalpha) expression in breast tumors are unclear, but studies suggest that they are partly at the level of transcription. We have focused on the transcription factors that regulate the ERalpha minimal promoter, which we have previously shown to reside within the first 245 bp of the 5'-flanking region of the gene. Within this region are several elements essential for full ERalpha promoter transcriptional activity, including a GC box and an imperfect E box. In earlier studies we demonstrated an essential function for the Sp1 family of transcription factors in the regulation of ERalpha expression. We have now identified both USF-1 and ERalpha itself as components of a multi-protein complex of transcription factors that interacts at the ERalpha minimal promoter and is essential for its full transcriptional activity. Electrophoretic mobility shift assays demonstrated that Sp1 and USF-1, but not ERalpha, bind directly to the ERalpha minimal promoter. We showed by GST pull-down assays that ERa is able to interact in vitro with USF-1, suggesting, in addition to a possible interaction between ERa and Sp1, a mechanism whereby ERalpha is able to interact with the protein complex. Combined exogenous expression of the components of the complex in MCF-7 breast cancer cells resulted in a synergistic effect on transactivation of the ERalpha minimal promoter, suggesting that the importance of the protein complex is in the interactions among the components. Based upon these findings, we propose a possible model for transcription from the ERalpha minimal promoter.