臺灣博碩士論文加值系統

Epigenetic代表任何不藉由改變DNA序列本身而能遺傳給下一代的現象稱之。一般相信它對於細胞內基因的表現、個體的發育及癌症的形成都有其貢獻。DNA甲基化、組蛋白的修飾、位子效應和RNAi等等都是它的範疇。而本篇論文的主題就是在研究甲基化DNA與組蛋白修飾之間的關係。DNA甲基化與組蛋白的修飾能促使染色體結構改變進而影響基因的表現。就最近的實驗結果顯示，DNA甲基化是組蛋白中H3甲基化的下游，而甲基化的DNA會被MBD蛋白辨認然後與其它蛋白結合形成histone deacetylase 複合體去改變組蛋白的修飾作用。這就是目前兩條甲基化DNA與組蛋白修飾之間的路徑。我們從基因資料庫中發現到四個基因【CLLD8、SETDB1、CG12196和R05D3.11】他們同時具有辨識甲基化DNA的domain和能甲基化組蛋白的domain。於是我們推測這可能是甲基化DNA與組蛋白修飾之間的另一條路徑。我們把這些基因的MBD表現在大腸桿菌的系統內然後用EMSA去測試它們的功能結果發現只有果蠅的基因CG12196 有功能，於是我們推論可能只有在果蠅中甲基化的DNA會藉由CG12196 這個基因去調節整體組蛋白甲基化。而這些基因能甲基化組蛋白的domain 我們也表現在大腸桿菌的系統中，然後藉由組蛋白甲基轉移實驗去測試其功能，結果我們發現他們都不具有把甲基轉移給組蛋白的能力。在未來我們打算把這些基因能甲基化組蛋白的domain 表現在baculoviruses的系統內在去測試它的是否具有把甲基轉移給組蛋白的功能。

Epigenetic means any heritable change in gene expression that is not caused by change in DNA sequence. As such it is believed to contribute to the gene expression in the cell and the normal processes of human development but also to aberrant disease states such as cancer. DNA methylation , histone modification , position-effect variegation and RNAi etc.. are all in this area. If we enhance understanding of the epigenetic will probably prove helpful diagnosis and treatment of some disease including cancer. Here we want to know the relationship between DNA methylation and histone modification.
DNA methylation and histone modification promoter change chromatin structure that may affect gene expression. In the recent experiments, they reveal the DNA methylation is downstream of the H3 methylation and DNA methylation can be recognized by the MBD, then recruit histone deacetylase complex to change the modification of the histone. They are two links between the sequential events of histone modification and DNA methylation. Here, we search database and find some genes (CLLD8, SETDB1,CG12196 and R05D3.11) containing both methyl CpG-binding domain and pre-SET/SET domain and they may be other link between DNA methylation and histone modification.In this study, we express their methyl CpG-binding domains in the E.coli system ,then testing their function by EMSA ; only the Drosophila gene CG12196 has the interaction. It reveals the Drosophila gene CG12196 may modulate the whole of histone methylation by the DNA methylation but other's gene can not. And we also express their pre-SET/SET domain in the E.coli system , then testing it's activity using histone methyltransferase assay ; but all genes do not have the activity.In the future, we will express their pre-SET/SET domain in the baculoviruses system and try again it have activity or not.

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