臺灣博碩士論文加值系統

抑癌蛋白p53 為細胞抗腫瘤生成機轉中一個重要的分子。當細
胞接觸到會致癌的危險因子時，p53 蛋白便會活化一系列其下游基
因的轉錄作用(transcription)，而這些下游基因的蛋白質產物，
則會進一步促使細胞走向細胞凋亡(apoptosis)、細胞週期停滯
(cell cycle arrest)或是DNA 修補(DNA repair)等路徑，其作用
在於避免細胞癌化及腫瘤產生。然而，由於其功能的表現皆與抑制
細胞增生有關，所以對一個正常或已修復的細胞而言細胞內表達過
多的p53 蛋白反而是一種傷害。因此，細胞內調控p53 的機制於是
顯得特別重要。目前已知，p53 活性的調控除了可經由轉錄後修飾
(post-translational modifications)、調整其在細胞內分佈位置
及改變其蛋白質穩定度等方式來調控外，p53 與其結合蛋白間的交
互作用亦會影響p53 的活性，如MDM2。
本實驗室的研究主題PIP，也是一個會與p53 結合的蛋白質，
且其蛋白質C 端有一可能與p53 蛋白降解有關的環指基團
(ring-finger motif)。因此，本論文想要探討的問題是PIP 蛋白
在細胞內表達後是否會影響到p53 抗腫瘤生成的功能。於實驗結果
中，透過分析細胞週期的變化，我們發現PIP 於細胞內表達後分別
會向下調節p53 所控制的G2/M 管制點或是抑制p53 所導致的細胞
凋亡現象。在H1299 細胞中，藉由向下調節p53 所調控的G2/M 管
制點，PIP 會造成停滯在G2/M 期的細胞數目減少，同時增加p53
所造成的G0/G1 期停滯現象; 然而在Saos-2 細胞中，PIP 的表達
則會有效地抑制p53 所產生的細胞凋亡現象因而增加停滯在G0/G1
期的細胞數目。此外，從報導基因分析與西方點墨分析的實驗結果
中得知，PIP 於細胞週期分析中，對H1299 與Saos-2 所造成的G0/G1
停滯現象與細胞內p21 蛋白表達量的增加沒有關係，反倒是在PIP
蛋白表達後，p53 蛋白在細胞內的含量會有減少的現象。因此，綜
合實驗所觀察到的現象與結果，我們認為PIP 是一個可影響並調整
p53 功能的p53 結合蛋白。

p53 is one of the most important tumor suppressors during carcinogenesis. In response to stress, cellular p53 protein becomes stabilized and activated. The activated p53 protects cells from oncogenic transformation mainly through activating the transcription of its downstream target genes, and subsequently, the p53-induced proteins implement its biological functions including cell cycle arrest, apoptosis and/or DNA repair. One of the major aspects in the field of p53 research is to unravel the molecular mechanisms by which the activities of p53 are regulated. To date, there are several well-documented pathways for regulating p53’s activity such as post-translational modifications, cellular distribution, protein stabilization and the interaction with its binding proteins. In our laboratory, we have cloned and characterized a p53-interacting protein, named PIP.
The focus of my research is to analyze and evaluate the cellular functions of p53 in response to the overexpression of PIP. There are two major observations obtained from the results of cell cycle analysis. Depending on the cellular context, the function of PIP is either to suppress the p53-induced apoptosis or to attenuate the G2/M checkpoint initiated by p53. In H1299 cells, PIP alleviates the G2/M checkpoint induced by p53, and subsequently, causes the accumulation of cells in G1 phase. On the other hand, in Saos-2 cells, a sturdy G1 arrest is observed in accompany with a significant diminishment of the apoptotic cells induced by p53. Based on reporter assay and Western blot analysis, the potentiation of G1 arrest induced by PIP, both in H1299 and Saos-2, is not due to the upregulation of p21, in turns, perhaps via downregulating the p53’s protein level.
In conclusion, according to the PIP’s effect we observed, mechanistically, PIP might counteract the cellular function of p53 either in apoptosis or in G2/M checkpoint possibly through altering p53’s degradation pathway as mdm2 does.

誌謝••••••••••••••••••••••••••••••••••••••••••••••••• Ⅰ
正文目錄•••••••••••••••••••••••••••••••••••••••••••••• Ⅱ圖文目錄•••••••••••••••••••••••••••••••••••••••••••••• Ⅲ
縮寫表••••••••••••••••••••••••••••••••••••••••••••••• Ⅴ
中文摘要•••••••••••••••••••••••••••••••••••••••••••••• Ⅵ
英文摘要•••••••••••••••••••••••••••••••••••••••••••••• Ⅷ
第一章、緒論••••••••••••••••••••••••••••••••••••••••••• 1
第二章、材料與方法••••••••••••••••••••••••••••••••••••• 7
第一節、實驗材料及相關儀器••••••••••••••••••••• 7
第二節、實驗方法••••••••••••••••••••••••••••••• 10
第三章、結果•••••••••••••••••••••••••••••••••••••••••• 16
第四章、討論•••••••••••••••••••••••••••••••••••••••••• 24
參考文獻•••••••••••••••••••••••••••••••••••••••••••••• 46

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