葡萄糖抑制作用現象存在許多微生物中，在Saccharomyces cerevisiae酵母菌中，當外在環境存有大量葡萄糖時，葡萄糖以外的碳源利用會受到轉錄抑制子MIG1蛋白參與的轉錄調控而被抑制，迫使酵母細胞優先使用葡萄糖，並抑制其它碳源的利用；當環境中的葡萄糖漸少時，SNF4蛋白會參與幫助解除葡萄糖抑制，回復葡萄糖以外之碳源的使用能力。近期研究顯示，在白麴菌Saccharomycopsis fibuligera中也存在葡萄糖抑制現象，白麴菌為一種具分泌大量外泌性酵素能力的酵母菌，其外泌性酵素的分泌會受到葡萄糖抑制作用影響，但有關白麴菌中參與葡萄糖抑制的相關基因研究非常稀少。為了尋找白麴菌中與葡萄糖抑制相關的基因，本研究利用S. cerevisiae酵母菌中參與葡萄糖抑制的相關基因與實驗室先前所建立的白麴菌基因體資料庫進行比對，找到了一段與S. cerevisiae SNF4具有66%相似度(identy)的核甘酸序列，並將其命名為sfSNF4，再以兩階段置換(two step swapping)的方式在S. cerevisiae酵母菌中表現sfSNF4，以瞭解S. cerevisiae酵母菌與白麴菌之間SNF4功能的相似程度。本研究首先建立了3株S. cerevisiae SNF4Δ的基因剔除株，接著再將這些基因剔除株的基因體中插入sfSNF4，得到S. cerevisiae SNF4Δ:: sfSNF4基因置換株。SNF4Δ之酵母菌由於缺乏SNF4蛋白，無法解除葡萄糖抑制，不能生長在非醱酵性碳源(3%甘油)的培養基中，所以我利用此現象進行功能性互補試驗(functional complementation assay)。實驗結果顯示在SNF4Δ:: sfSNF4酵母菌菌株中，細胞內表現的sfSNF4依舊無法回復SNF4Δ酵母菌菌株使用非醱酵性碳源的能力，然而有趣的是，外來的sfSNF4會導致S. cerevisiae在YPD中生長速度變慢，其世代週期(doubling time)為2.96±0.17(hrs)，與野生型1.44±0.02(hrs)或SNF4Δ菌株1.67±0.04(hrs)相比，具有顯著差異(P=0.004<0.05；P=0.006<0.05)；若在SNF4Δ:: sfSNF4菌株中表現帶有酵母菌SNF4的pRS413-scSNF4表現載體，其世代週期為2.99±0.35(hrs)，與SNF4Δ:: sfSNF4菌株相比沒有顯著差異(P=0.924>0.05)；此外，pRS413-scSNF4表現載體可以拯救S. cerevisiae SNF4Δ基因剔除株使用非發酵性碳源(甘油)的能力而生長在含3%甘油的YPG培養基中，然而在S. cerevisiae SNF4Δ:: sfSNF4基因置換株中卻無法觀察到此現象；綜合以上的結果顯示，白麴菌sfSNF4和酵母菌S. cerevisiae scSNF在功能上具有差異，外來的sfSNF4可能會擾亂S. cerevisiae酵母菌中葡萄糖抑制的基因表現調控，而影響葡萄糖代謝並導致生長延遲。

Glucose repression occurs widely in fungi and bacteria. When glucose is present in the medium, the genes required for the utilization of alternative carbon sources are repressed, transcribed at low level or not at all. In yeast Saccharomyces cerevisiae, Snf4p is required for derepression of glucose-suppress genes in response to glucose depletion. Previous studies suggested that glucose repression is also present in yeast Saccharomycopsis fibuligera which has many applications in industries. By 454 sequencing and sequence similarity analysis, we identify a putative SNF4 gene of S. fibuligera, sfSNF4 which has 66% nucleotide sequence identities with S. cerevisiae SNF4. To understand the functional similarity of S. cerevisiae SNF4 and S. fibuligera SNF4, we use two-step swapping procedures to replace S. cerevisiae SNF4 gene with sfSNF4. We obtained 3 independent S. cerevisiae SNF4Δ:: sfSNF4 clones which the SNF4 gene was replaced by sfSNF4. However, the replacement of S. cerevisiae SNF4 with sfSNF4 dose not rescue the genetic defect of losing the SNF4 gene in S. cerevisiae for not been able to grow with non-fermentable carbon source. Interestingly, cells of S. cerevisiae SNF4Δ:: sfSNF4 grow poorly in glucose containing nutrient media (YPD) compare to wild type S. cerevisiae and shows obvious growth defect compare to wild type S. cerevisiae and S. cerevisiae SNF4Δ. We believe that the expression of sfSNF4 gene may interfere with the glucose metabolism of S. cerevisiae by disrupting the expression regulation of glucose repression. Our results suggest that there might be functional differences between S. cerevisiae SNF4 and S. fibuligera SNF4.

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