在調節細胞鋅離子恆定中鋅離子運輸蛋白2 (ZnT-2)扮演了重要的角色，當細胞遭受過多鋅離子時，ZnT-2會將過多的鋅離子儲存至胞器與排泄小泡內，降低細胞內鋅離子含量。本篇的研究將探討人類ZnT-2 (hZnT-2)的基因調控機制。我們細胞處理鋅之後發現hZnT-2表現會隨著劑量以及時間上升，此外，鎘也可以誘導hZnT-2表現。當在細胞內大量表現金屬感應轉錄因子(MTF-1)時，hZnT-2表現會增加；降低MTF-1表現則會抑制hZnT-2表現，由此可知MTF-1會調控hZnT-2基因。我們於hZnT-2基因啟動子上發現了5個可能的金屬感應序列(MRE)，然而經過不同片段啟動子分析後發現hZnT-2啟動子必須至少擁有兩個MRE才能被鋅誘導。然而經由點突變分析，發現MREb是唯一可以被鋅誘導的MRE。除了MRE以外，我們在接近MREc的位置發現了zinc-finger E-box binding homeobox (ZEB)的結合位置，將此結合位置突變或者刪除後可以增加hZnT-2啟動子活性。當降低ZEB-1的表現時，可以增加hZnT-2基因表現；大量表現ZEB-2時可以抑制hZnT-2表現。然而大量表現ZEB-1與降低ZEB-2表現對hZnT-2並不影響。從這些結果顯示，MTF-1可以增加hZnT-2表現，但ZEB會抑制hZnT-2表現。

Zinc transporter 2 (ZnT-2) is one of the cellular factors responsible for Zn homeostasis. Upon Zn overload, ZnT-2 transports Zn into excretory vesicle to reduce cellular Zn. We investigated in this study the molecular mechanism involved in the regulation of human ZnT-2 (hZnT2) gene. When treated with Zn, hZnT-2 gene expression increased in a dose- and time-dependent manner. Besides to Zn, Cd is also a potent inducer of the gene. Metal response element (MRE)-binding transcription factor 1 (MTF-1) regulated hZnT-2 expression since over-expression of MTF-1 increased the transcription whereas knock-down of MTF-1 reduced the expression. Analysis of the hZnT-2 promoter region revealed that five putative MREs are present. A series deletion of the promoter region was conducted to investigate the MREs required for Zn induction. The result showed that at least two MREs were required. Mutation for each MRE was also performed to evaluate the significance of individual MRE for Zn induction. Surprisingly, only one MRE (MREb) is sufficient for the metal induction. Besides to MREs, a sequence for zinc-finger E-box binding homeobox (ZEB) binding is present next to MREc. Mutation or deletion of the ZEB biunding site resulted in an increase of the basal and induced hZnT-2 promoter activity. Knock-down of ZEB-1 increased the expression of hZnT-2, and over-expression ZEB-2 reduced hZnT-2 expression. However, over-expression ZEB-1 or knock-down of ZEB-2 did not affect hZnT-2 expression. Results from this study show that MTF-1 stimulates but ZEB represses the expression of hZnT-2 under Zn overload.

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