金屬硫蛋白（metallothionein，MT）是細胞內維持金屬環境衡定的一個小分子，在早期的研究中觀察到MT的表現與細胞增生的關聯性，且其表現量也與細胞週期有關。而本實驗在探討MT的轉錄因子MTF-1（metal-regulatory transcription factor-1）是否在細胞週期的不同階段中會有所差異。我們建立了一株穩定表現His-tagged MTF-1的CHO-K1細胞，再去觀察不同細胞週期的MTF-1有無改變，結果發現當細胞以50 ng/ml colcemid或0.1 μg/ml nocodazole處理16小時而使其停滯在metaphase時，MTF-1會有後修飾作用，並且利用λ phosphatase證明此作用為磷酸化。若以serum depletion和aphidicolin之處理使細胞停滯於G1/S transition再同步進入細胞週期，也可以觀察到在G2/M phase附近有磷酸化MTF-1的出現。接著在處理了不同的kinase inhibitors實驗裡，我們發現p38、ERK和JNK並沒有參與在M phase的MTF-1磷酸化過程中，然而Cdk1抑制劑卻使得colcemid造成的mitotic cells比例下降，MTF-1磷酸化程度亦隨之減少。而我們以免疫沈澱法無法觀察到Cdk1與MTF-1有直接的交互作用。綜合以上結果，我們認為MTF-1的磷酸化與M phase有其關聯性。

Metallothionein (MT) is a small molecule that regulates the intracellular metal homeostasis. In the early researches, MT was found to be linked to cell proliferation and its expression is cell cycle-dependent. In the present study, we investigated the correlation between cell cycle and the expression of MTF-1 (metal-regulatory transcription factor-1), which regulates MT gene transcription. We established a cell line stably expressing His-tagged MTF-1 in CHO-K1 cells. By using 50 ng/ml colcemid or 0.1 μg/ml nocodazole to arrest cells at metaphase, we observed a modification of MTF-1, which is proved to be phosphorylation. When combining serum depletion and aphidicolin treatment to arrest cells at G1/S boundary, followed by synchronously progression, phosphorylation of MTF-1 around the G2/M phase can be observed. Several kinase inhibitors were used to examine the possible involvement of kinase cascades in the mitotic phosphorylation of MTF-1. The p38, extracellular signal-activated protein kinase (ERK) and the c-Jun N-terminal kinase (JNK) cascades did not appear to be involved in the mitotic phosphorylation of MTF-1. The phosphorylation level was decreased with the co-treatment of colcemid and Cdk1 inhibitor (roscovitine). However, no direct interaction between Cdk1 and MTF-1 can be found as demonstrated by immunoprecipitation assay. These results suggest a link between mitosis and the phosphorylation of MTF-1.

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