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標題: | 酵母菌Msz1蛋白功能之研究 Characterization of the yeast Msz1 protein |
作者: | Ya-Yun Wang 王雅筠 |
出版年 : | 2001 |
學位: | 碩士 |
摘要: | Zip1是酵母菌中一個在減數分裂特定表現的蛋白質,它是聯會複合體(synaptonemal complex)中央區域(central region)的重要結構蛋白。當酵母菌缺少此一蛋白質時,即在zip1突變株中,同源染色體(homologous chromosomes)不能進行聯會(synapsis),染色體之間的互換無法完成,而減數分裂的進行則被粗絲期檢控點(pachytene checkpoint)所阻止,使得細胞停留(arrest)在減數分裂前期(prophase)中的粗絲期,無法繼續進行減數分裂來產生四個孢子。可是當MSZ1基因在zip1突變株中大量表現時,卻可以使此突變株繼續進行減數分裂而產生孢子。為了更進一步瞭解Msz1蛋白質的性質和可能的功能,以及使zip1進行減數分裂的分子機制,於是在Msz1蛋白的C端(C terminus)加上抗原決定基的標籤(epitope tagging),藉以方便進行蛋白質性質的分析。 由蛋白質免疫轉印(Western blot analysis)實驗結果可得知,Msz1蛋白質並不只在減數分裂中特定表現,但它的表現量會隨著細胞進入減數分裂後而增加。而Msz1蛋白質在野生種(wild type)與zip1突變株的表現情形及模式並沒有明顯差別。將Msz1蛋白質序列與其他物種的蛋白質序列進行比對發現,其與一些染色體蛋白(chromosome-associated proteins)具有同源性(homology),此比對結果顯示,Msz1蛋白質有可能也是個染色體蛋白。經由細胞遺傳學的實驗方法證實,Msz1蛋白質的確位於染色體上,並呈現點狀分佈。 另外,經由遺傳學實驗證實,一個與姊妹染色分體之間互換(sister-chromatid recombination)有關的基因,RAD54,可能參與了藉大量表現MSZ1使zip1進行減數分裂的分子機制。 The yeast meiosis-specific protein Zip1 is a major structural component of the central region of the synaptonemal complex (SC). In the absence of Zip1, chromosomes fail to synapse and recombination intermediates (Holliday junctions) accumulate, resulting in checkpoint-mediated arrest at the pachytene stage of prophase. YGR042w, an unidentified yeast ORF, was previous isolated as a multicopy suppressor of zip1 in sporulation, and was named as MSZ1. When MSZ1 is overexpressed in zip1 mutants, sporulation is partially restored. Using epitope-tagging method, the Msz1 protein was detected by Western blot analysis. The result of time course analysis indicated that Msz1 is not a meiosis-specific protein, but its expression is induced in meiosis and peaks around pachytene. Based on the amino-acid sequence analysis, Msz1 has homology with some chromosome-associated proteins. To verify if Msz1 is also associated with chromosomes, immunolocalization experiments were performed. The results of cytological analyses indicated that the Msz1 protein is a nuclear protein. It is localized to pachytene chromosomes as distinct foci. The chromosomal localization of Msz1 provides an important clue for the study of Msz1 function(s) and pachytene checkpoint machinery. Additionally, when RAD54, a gene involved in sister-chromatid recombination, is deleted in zip1 cells overproducing Msz1, the sporulation frequency was greatly reduced. This result suggests that sister-chromatid repair appears to be involved in the Msz1-mediated suppression pathway. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/75237 |
全文授權: | 未授權 |
顯示於系所單位: | 植物科學研究所 |
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