Set7作用於DNA損壞修復及細胞週期管制調控路徑功能之探討

Abstract

Set7為Saccharomyces cerevisiae的細胞核內蛋白，Set7蛋白擁有一個具有甲基轉移酶活性的SET-domain，然而Set7在細胞之中所作用的受質在目前還是未知的，而在先前的研究中，我們實驗室藉由酵母菌雙雜合實驗中發現到SETD6―Set7於人類中的直系同源蛋白能夠與NBS1存在結合作用，並且set7剔除的酵母菌具有較高的methyl methanesulfonate耐受能力，因此我分析Set7參與在可能的DNA損壞修復以及細胞週期管制調控的路徑為何，而在DNA損壞抵抗能力試驗中，set7 mec1剔除的酵母菌相較於mec1剔除的酵母菌顯現有較高的hydroxyurea與methyl methanesulfonate耐受能力，而將一野生型SET7基因補回送入set7 mec1剔除的酵母菌中，發現造成對於hydroxyurea與methyl methanesulfonate耐受能力降低並且變得與mec1剔除的酵母菌耐受能力接近，從此結果暗示Set7與細胞週期管制調控的信息傳遞有所關連，因此我推測Set7能夠調控某種參與在MEC1下游信息傳遞路徑的蛋白功能，除此之外我也將辨別出Set7所作用的受質為何以及確認Set7中甲基轉移酶活性位置

Set7 is a nuclear protein in Saccharomyces cerevisiae, which contains a SET-domain encoding the methyltransferase activity. However, the function and cellular substrates of Set7 are still elusive. Form the previous study in our lab, we demonstrated SETD6, a Set7 ortholog of human, interacts with NBS1 in a yeast two-hybrid assay. And the set7 knockout strain displayed higher resistance to methyl methanesulfonate treatment. Here I dissected the potential pathway of Set7 in DNA repair and cell cycle checkpoint. In the spotting assay, the set7 mec1 knockout strain showed higher resistance to hydroxyurea and methyl methanesulfonate than those in the mec1 knockout strain. When a wild type SET7 gene was complemented in the set7 mec1 strain, the resistance to hydroxyurea or methyl methanesulfonate recovered to that of the mec1 strain. These results indicate that Set7 is involved in cell cycle checkpoint signaling. Therefor I speculate that Set7 could modulate a protein at the downstream of the MEC1 signaling pathway. Furthermore,I will identify the potential substrate of Set7 and Set7 methyltransferase activity site.