有文獻報導指出，轉錄因子的修飾對基因調控是重要的。在近年來我們實驗室的研究中，已發現當A431細胞處理EGF時，其能夠藉由活化Ras-ERK及Ras-Rac-JNK等路徑來誘導12(S)-lipoxygenase基因的表現，並且也可增加c-Jun的生合成。除此之外，我們發現12(S)-lipoxygenase promoter上並沒有AP1結合位置，但過度表現c-Jun時能夠誘導12(S)-lipoxygenase基因的表現，並且c-Jun/Sp1 interaction對12(S)-lipoxygenase基因的表現是很重要的。於是我們便有興趣來探討調控c-Jun/Sp1 interaction的機制為何。當細胞處理phosphatase抑制劑（cyclosporin A及cantharidin）時，發現這些抑制劑會抑制掉EGF誘導的12(S)-lipoxygenase mRNA表現及酵素活性；除此之外，這些抑制劑還能抑制EGF誘導的c-Jun/Sp1 interaction，但對c-Jun的生合成並沒有影響。由以上結果可知，c-Jun/Sp1 interaction可能會受到磷酸化與去磷酸化的調控。之前文獻曾報導過TAM-67，其為將c-Jun N端 truncated的突變型，可以和Sp1產生交互作用，我們便推測c-Jun C端的去磷酸化對調控c-Jun/Sp1 interaction可能扮演一個重要的角色。我們利用myc- TAM-67來探討是否EGF會誘導c-Jun C端進行去磷酸化。在免疫沉澱實驗中，我們發現EGF會誘導myc- TAM-67進行去磷酸化，且去磷酸化現象會隨著EGF處理時間增加而更明顯。綜合以上結果，我們可以知道，EGF會誘導c-Jun C端進行去磷酸化，以促使c-Jun和Sp1產生交互作用，進而促使12(S)-lipoxygenase基因的表現。

It is reported that modification of transcriptional factor is important for gene regulation. In recent years, we have found that EGF induces 12(S)-lipoxygenase gene expression via activation of Ras-Rac-JNK and Ras-ERK pathways in A431 cells, and also increases c-Jun biosynthesis. Furthermore, We found that 12(S)-lipoxygenase promoter without AP1 consensus binding site is induced by c-Jun overexpression, and the c-Jun/Sp1 interaction plays an important role in EGF-induced 12(S)-lipoxygenase gene expression. Therefore, we are interested in studying the regulation of c-Jun/Sp1 interaction. When A431 cells were treated with phosphatase inhibitors（cyclosporin A and cantharidin）, the effect of EGF-induced expression of 12(S)-lipoxygenase mRNA and enzyme activity was inhibited. Furthermore, cyclosporin A and cantharidin also inhibited the interaction between c-Jun and Sp1 in EGF-treated cells while EGF-induced c-Jun biosynthesis was not affected. These results indicated that the interaction between c-Jun and Sp1 might be regulated by a phosphorylation/dephosphorylation mechanism. It was previously reported that TAM-67, which is c-Jun N-terminus truncated form, could interact with Sp1, and suggested that c-Jun C-terminus dephosphorylation may play an important role in the regulation of c-Jun/Sp1 interaction. We used myc-TAM-67 to study that whether EGF induces c-Jun C-terminus dephosphorylation. In immunopreciptation assay, we found that EGF induced dephosphorylation of myc-TAM-67 in a time-dependent manner. Taken together, EGF induces c-Jun C-terminus dephosphorylation and promotes c-Jun/Sp1 interaction, followed by the activation of 12(S)-lipoxygenase gene expression.

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