- 學位論文
砷對金屬感應轉錄因子運輸及代謝的影響
Effect of arsenic treatment on the trafficking and metabolism of metal responsive transcription factor 1
摘要
金屬感應轉錄因子 (MTF-1) 用於調控體內的金屬恆定和對抗氧化壓力基因的表現。MTF-1主要分布在細胞質，在鋅或鎘刺激下，MTF-1會從細胞質進入細胞核，進而和啟動子結合轉錄下游基因。在本研究中發現MTF-1也透過砷的誘導進入細胞核活化下游基因，細胞質MTF-1隨著砷暴露時間增加而減少。另一方面，細胞核MTF-1在砷刺激1小時達到最高，而後隨時間增加而減少。在螢光影像中顯示MTF-1受砷刺激先在細胞核產生蛋白質聚集，之後被送到細胞質。值得注意的是，MTF-1需進入細胞核才能在砷誘導下形成蛋白質聚集，當透過突變的方式誘使MTF-1無法進核將抑制蛋白質聚集。而且在NES突變的實驗發現MTF-1蛋白質累積在細胞核。我們推斷砷的刺激下細胞核MTF-1和PML產生交互作用，形成聚集的現象，並改變下游的基因表現量。利用PML正常或缺失的MEF細胞處理鋅、鎘或砷，都可以發現到MTF-1下游基因表現在PML缺失的細胞中會顯著的下降，此結果顯示PML對MTF-1的活性有影響力。
並列摘要
Metal responsive transcription factor 1 (MTF-1) regulates the expression of genes involving in metal homeostasis and anti-oxidative stress. MTF-1 locates mainly in cytoplasm. With the stimulation of cadmium or zinc, MTF-1 translocates into nucleus and binds to the promoter of target genes. We found that MTF-1 can also be activated by arsenic (As) treatment and moves into nucleus. Analysis of the cytoplasmic MTF-1 reveals that the protein level decreased with As exposure time. On the other hand, nuclear MTF-1 increased within 1 h of As treatment, but decreased afterward. Image analysis indicates that MTF-1 aggregates in the nucleus and the aggregates trafficked back to cytoplasm with As treatment. Noticeably, As-induced MTF-1 aggregation occurred only when the protein translocated into nucleus. There was no aggregates occurred for the MTF-1 mutants that failed to enter the nucleus with As treatment. Noticeably, the aggregated MTF-1 retained in the nucleus once the nuclear export signal was destructed. Using wild type and PML-null MEF cells to treated with Cd, Zn or As showed that MTIIA expression was dramatically reduced in the PML-null MEF cells. The result indicates that PML is regulated to integral MTF-1 activity. However, whether PML is required for the trafficking of MTF-1 under As stress remains unknown.