葡萄糖對於許多微生物而言是良好的碳源，所以不少微生物處於富含葡萄糖的環境下，為了優先利用葡萄糖，會去抑制其他碳源代謝的基因表現，此種現象稱之為葡萄糖抑制作用(glucose repression)，當釀酒酵母菌Saccharomyces cerevisiae處在富含葡萄糖的環境之下，藉由細胞內轉錄抑制子Mig1p來抑制某些下游的基因轉錄，使S. cerevisiae能優先利用葡萄糖，當葡萄糖的濃度大幅降低以後，蛋白質激酶Snf1p會被磷酸化並進入細胞核內，細胞核內的Mig1p則會被Snf1p磷酸化，接著被磷酸化的Mig1p會被送到細胞核外，便不會再抑制相關基因的表現(如其他碳源利用的基因)，讓S. cerevisiae能開始利用其他碳源。除了S. cerevisiae有葡萄糖抑制作用的現象外，根據前人研究指出，白麴菌Saccharomycopsis fibuligera也同樣有葡萄糖抑制作用的現象，白麴菌本身是一種具有外分泌酵素的酵母菌，好比澱粉水解酶(amylase)，而這些外分泌酵素的活性也受到葡萄糖抑制作用的影響而被抑制，儘管如此，有關於白麴菌葡萄糖抑制作用的相關研究並不多。為了瞭解白麴菌葡萄糖抑制作用的相關調控機制，本研究在先前所建立的白麴菌基因體資料庫與S. cerevisiae酵母菌參與葡萄糖抑制作用的相關基因進行比對，發現與S. cerevisiae MIG1相似的DNA序列以及有較為保守的蛋白質序列，我將其命名為sfMIG1，較保守的蛋白質序列為 S. cerevisiae MIG1與sfMIG1的Cys2-His2 鋅指模體(zinc-finger motif)。所以我想了解兩個物種MIG1基因功能上的異同，便將S. cerevisiae的MIG1基因剔除掉，再讓sfMIG1轉形(transformation)進S. cerevisiae裡，讓白麴菌的MIG1在S. cerevisiae表現，來觀察其功能性的變化。有趣的是，當我們把S. cerevisiae的MIG1基因剔除 (KO)或將sfMIG1基因置入 (KI) S. cerevisiae裡面，生長速率都沒有受到太大的影響，接著將這些菌株點菌在非葡萄糖碳源並含有2-deoxyglucose (2DG)的培養基上，讓酵母菌處於葡萄糖抑制作用卻無法利用葡萄糖的環境，在YPS (yeast peptone sucrose)與YPG(yeast peptone glycerol)的盤子上，KO菌株生長得比野生株和KI菌株還快，這也意味，KI菌株有恢復葡萄糖抑制的作用，另一方面，將這些菌株培養在葡萄糖環境與非葡萄糖環境的兩種條件下，再抽RNA並進行real-time PCR，檢測一些受Mig1p調控的下游基因之相對表現量，發現KI菌株的SUC2、HXT4和EMI2基因相對表現量較接近野生株，而KO菌株的基因相對表現量比起野生株或KI菌株來得高，但KI突變株又比野生株稍高，所以KI突變株的sfMig1p的確有部份補償(compensate) S. cerevisiae的Mig1p功能，但其中一個受S. cerevisiae Mig1p抑制的下游基因REG2，KI突變株與KO突變株沒有顯著性差異並且比野生株的相對表現來得高，綜合以上的結果顯示， sfMig1p並不影響S. cerevisiae的生長，在葡萄糖抑制作用的實驗可以補償S. cerevisiae Mig1p的功能，但在real-time PCR抑制下游基因的表現只可部份補償抑制效果，而在REG2這個基因卻無補償現象，這也意謂兩者的Mig1p蛋白依然存在著一些功能性的差異，導致抑制基因的表現不完全或無法抑制，而可能的原因是蛋白質結構上的差異造成與其他蛋白質或DNA結合的程度有所差異。

Glucose is the most preferred carbohydrate source in yeast. When glucose is present, genes are responsible for metabolizing other sugars will be suppressed and this phenomenon has been termed glucose repression. Mig1p is the major transcription factor that is a Cys2-His2 type of zinc-finger protein and responsible for the glucose repression in yeast. When S. cerevisiae is exposed to high glucose concentrations, Mig1p is not phosphorylation state and is located in the nucleus to represses the target genes by binding to the promoters of the genes. When S. cerevisiae is exposed to low glucose concentrations, Mig1p is phosphorylated through the Snf1p mediated signal transduction cascades and is translocated from nucleus to cytoplasm to cause the genes expression which are repressed by Mig1p. Otherwise, Mig1p is not only suppressing alternative sugars but also suppressing other genes. Mig1p is global regulation transcriptor in S. cerevisiae. Previous studies indicated that glucose repression phenomenon was observed in S. fibuligera. However, the role played by Mig1p homologous of S. fibuligera is still not clear. In this study, we compared the sequence similarity between Saccharomyces cerevisiae MIG1 and S. fibuligera MIG1 genes, and we replaced the S. cerevisiae MIG1 gene with S. fibuligera MIG1 gene to gain more information on the functionality of S. fibuligera MIG1 gene. Doubling time is no difference between wild type, KO mutants (knock out S. cerevisiae mig1), and KI mutants (knock in S. fibuligera MIG1). Spot assay in YPS or YPG contains 2-deoxyglucose; KO grew well than wild type and KI mutants. In real-time PCR, KO mutants’ gene expressions are higher than KI mutants or wild type for SUC2, HXT4 and EMI2. But it’s no difference between KO mutants and KI mutants for REG2. Based on the above, there are some different functions between S. cerevisiae Mig1p (scMig1p) and S. fibuligera Mig1p (sfMig1p).

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