自從人類基因組被定序以來，生命科學的研究主流已經從基因轉成蛋白質體學的領域。對於蛋白質上的修飾調控的相關研究遂成為21世紀生命科學最大的研究方向。例如近年來，組蛋白的離胺酸甲基化作用已被得知在基因的表現及染色質的重建上具有決定性的調控行為。 基因體標註顯示尚有許多未知活性與功能的甲基轉移酶，故本研究利用啤酒酵母菌（Saccharomyces cerevisiae）上面的開放讀碼框BUD23及NNT1具有甲基轉移酶的特徵序列的特性，來進行對於甲基轉移酶的相關研究。 BUD23又稱為YCR047C，在酵母菌基因資料庫當中被認為具有參與酵母菌出芽生殖的相關作用，是在整個酵母菌細胞週期當中具有非常重要的地位。 而NNT1也就是YLR285W，具有rDNA silencing以及決定此酵母菌壽命的作用。此基因產物可能為一nicotinamide N-methyltransferase。本篇研究就是要證明這兩個掌控酵母菌生與死的基因本身具有甲基轉移酶的活性。 Since human DNA sequencing is complete, the main areas of life science shift from genomics turn to proteomics. The study of post-translational modification of proteins dominates the research direction of 21st century life science. For example, recently the lysine methylation of histone has been found to play an important role in regulating gene expression and chromatin remodeling. Because genome annotation has shown a variety of methyltransferase genes of which the activity and function are still unclear, so in this investigation, I studied two the open reading frames in the yeast genome: YLR285W and YCR047C of Saccharomyces cerevisiae, both of which have been inferred as a methyltransferase by sequence comparison. YCR047C, also called BUD23, has been shown to be involved in bud-site selection of Saccharomyces cerevisiae. It is an important gene for yeast cell cycle. YLR285W, also known as NNT1, may encode a nicotinamide N-methyltransferase in yeast. This enzyme has a role in rDNA silencing and in lifespan determination. This study is aimed to prove the methyltransferase activity of these two putative enzymes which control the life and death of yeast.
