荷爾蒙 1α, 25-dihydroxyvitamin D3 (1,25(OH)2D3)對於細胞生理機能的調控佔有重要的地位，包括鈣磷離子的?琠w、細胞生長、分化、細胞凋亡等。1,25(OH)2D3藉由與1,25(OH)2D3 receptor(VDR)的結合，促進VDR與retinoid X receptor(RXR)形成heterodimer複合物，進而去活化或抑制目標基因轉錄、轉譯的活性。文獻指出，VDR蛋白質目前已知的轉譯後修飾作用，包含磷酸化及ubiquitination，且影響其目標基因轉錄活性或蛋白質的穩定性。在本論文中，我們發現VDR蛋白質的SUMOylation轉譯後修飾作用，是由SUMO-2所造成的，且VDR主要的SUMOylation位置在離胺酸-103。經由promoter activity assay，結果發現VDR經由SUMOylation後，會增加VDR/RXR所調控目標基因的轉錄活性；另外，在mRNA層面，當離胺酸-103突變成丙胺酸後，會減少1,25(OH)2D3所導致osteopontin mRNA的表現。利用ChIP實驗，證實VDR蛋白質野生型與SUMOylation突變型，其對osteopontin promoter的DNA結合能力相似。總而言之，實驗結果顯示VDR的SUMOylation，可能會藉由影響VDR與co-activators的結合能力，進而影響其調控目標基因的轉錄活性。

The 1α, 25-dihydroxyvitamin D3 (1,25(OH)2D3) is involved in various physiological processes, including calcium/phosphorous homeostasis, cell growth, differentiation and apoptosis. 1,25(OH)2D3 induces the formation of VDR/RXR complex to up-regulate or down-regulate target gene expression. Recent studies find that VDR undergoes several post-translational modifications, such as phosphorylation and ubiquitination, which may regulate its transcriptional activity and/or stability. In this study, we identified VDR as a new target for small ubiquitin-related modifier (SUMO)-2 modification in vitro. In E. coli. SUMO-conjugation system, VDR is mainly sumoylated at Lys-103. SUMOylation of VDR enhanced VDR/RXR-mediated transcriptional activation as determined by promoter activity assay. In addition, 1,25(OH)2D3-induced expression of osteopontin was attenuated after mutation of VDR SUMOylation site. However, chromatin immunoprecipitation assay indicated that wild type and K103A mutant of VDR bound to the osteopontin promoter with similar affinity. Collectivity, our results suggest that SUMOylation of VDR may affect its transcriptional activity by modulating the interaction between VDR and co-activators.

致謝詞 ………………………………………………………. 3
中文摘要 ……………………………………………………. 4
英文摘要 ……………………………………………………. 5
縮寫表 ………………………………………………………. 6
序言 …………………………………………………………. 7~10
研究動機 ……………………………………………………. 11
實驗材料 ……………………………………………………. 12~15
實驗方法 ……………………………………………………. 16~41
結果 …………………………………………………………. 42~45
討論 …………………………………………………………. 46~49
結論 …………………………………………………………. 50
參考文獻 ……………………………………………………. 51~54
圖表 …………………………………………………………. 55~63
附錄 …………………………………………………………. 64~68

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