Specificity Protein 1 (Sp1) Oscillation Is Involved in Copper Homeostasis Maintenance by Regulating Human High-Affinity Copper Transporter 1 Expression
Specificity Protein 1 (Sp1) Oscillation Is Involved in Copper Homeostasis Maintenance by Regulating Human High-Affinity Copper Transporter 1 Expression
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DOI：
10.1124/mol.111.076422
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发表时间：
2012-03-01
影响因子：
3.6
通讯作者：
Kuo, Macus Tien
中科院分区：
文献类型：
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作者：
Liang, Zheng D.;Tsai, Wen-Bin;Kuo, Macus Tien
铜是细胞生长的必需微量营养素，但过量是有毒的。铜转运蛋白（Ctr 1）在哺乳动物细胞中调节足够的铜水平中起重要作用。我们以前已经表明，表达的人高亲和力铜转运蛋白（hCtr 1）是转录上调铜耗尽条件下和下调下充满条件下，此外，hCtr 1水平升高抑制hCtr 1的表达。特异性蛋白1（Sp1）在铜胁迫条件下调节hCtr 1的表达。在本研究中，我们做了以下重要的观察：1）Sp1的表达在铜充足的条件下下调，但在铜缺乏的条件下上调。Sp1的这些上调和下调反过来又调节hCtr 1的表达，以控制铜稳态。2)铜调节的Sp1表达涉及Sp1结合到其自身的启动子所示的染色质免疫沉淀试验，因此，Sp1也转录自我调节通过hCtr 1/铜中介。3)Sp1的锌指和富含谷氨酰胺的反式激活结构域都参与了铜胁迫对Sp1介导的hCtr 1和Sp1的调控。4)虽然Sp3的表达也受到铜的利用率的调节，但Sp3不调节hCtr 1的稳态。总的来说，我们的研究结果表明，哺乳动物细胞使用Sp1振荡响应铜的可用性，以调节铜稳态通过hCtr 1的表达在一个三方的相互调节关系。这些发现对哺乳动物铜的生理调控具有重要意义。
Copper is an essential micronutrient for cell growth but is toxic in excess. Copper transporter (Ctr1) plays an important role in regulating adequate copper levels in mammalian cells. We have shown previously that expression of the human high-affinity copper transporter (hCtr1) was transcriptionally up-regulated under copper-depleted conditions and downregulated under replete conditions; moreover, elevated hCtr1 levels suppress hCtr1 expression. Specificity protein 1 (Sp1) regulates expression of hCtr1 under copper-stressed conditions. In this study, we made the following important observations: 1) Sp1 expression is down-regulated under copper-replete conditions but up-regulated under copperdepleted conditions. These up-and down-regulations of Sp1 in turn regulate hCtr1 expression to control copper homeo-stasis. 2) Copper-regulated Sp1 expression involved Sp1 binding to its own promoter as demonstrated by the chromatin immunoprecipitation assay; therefore, Sp1 is also transcriptionally self-regulated via hCtr1/ copper intermediation. 3) Both zinc finger and glutamine-rich transactivation domains of Sp1 are involved in the Sp1-mediated hCtr1 and Sp1 regulation by copper stresses. 4) Although Sp3 expression is also regulated by copper availability, Sp3 does not regulate hCtr1 homeostasis. Collectively, our results demonstrated that mammalian cells use Sp1 oscillation in response to copper availability to regulate copper homeostasis through hCtr1 expression in a tripartite inter-regulatory relationship. These findings have important implications in mammalian copper physiology regulation.