探討PDX1與Dnmt1之間的交互作用

Characterization of the interaction between PDX-1 and Dnmt1

邱子軒(Tzu-Hsuan Chiu)

指導教授 ： 江明格

國立中正大學/理學院/生命科學系分子生物研究所/碩士(2015年)

摘要

在胰臟的發育過程中受許多的轉錄因子調控著，例如：PDX1、Ptf1a、Ngn3等等，這些轉錄因子在胰臟發育過程中調控著細胞的分化，先前的文獻中提到PDX1對於胰臟的發育以及β-cells的成熟是必須的，我們實驗室先前利用yeast two hybrid assay，以PDX1當作誘餌，發現Dnmt1 (DNA methyltransferase 1)片段為1509-1590的蛋白質會與PDX1有交互作用，Dnmt1在哺乳類中為一個酵素能夠將甲基轉移至DNA上，而在發育的過程中，DNA上的甲基化能夠改變基因的表現以確保細胞往正確方向來分化。在過去的文獻中有發現當剔除Dnmt1後導致Arx基因受到影響，而使得胰臟發育和β-cells分化出現問題。在我的研究中，我建構表達Dnmt1不同區域的蛋白的質體，包含Dnmt1 (aa.1-555)、(aa.556-1103)、(aa.1124-1619)和 (aa.1124-1619Δ1509-1590)，利用GST-pull down assay證明Dnmt1 (aa.1509-1590)片段會與PDX1有專一性的交互作用，另外我也利用shDnmt1慢病毒去感染胰臟中的細胞株使Dnmt1表現量下降，並觀察到insulin的表現量下降。而後續實驗我打算利用CHIP assay去了解Dnmt1是否會結合到Arx啟動子上，以及降低PDX1的表現量後是否會影響到Dnmt1結合到Arx啟動子上的能力。

關鍵字

PDX1 ； Dnmt1 ； 胰臟發育

並列摘要

The pancreatic development requires many transcription factors, such as PDX1, Ptf1a, and Ngn3. These transcription factors can regulate cell differentiation during pancreatic development. Previous studies have shown that PDX1 is necessary for pancreatic development and β-cell maturation. Our laboratory has used the yeast two-hybrid assay to find that PDX1 could interact with Dnmt1 (DNA methyltransferase 1) protein(aa1509-1590). Dnmt1 is an enzyme that can transfer methyl group to DNA. During development, DNA methylation can cause changes in gene expression to make sure that the cell will properly differentiate. Previous studies have shown that loss of Dnmt1causes the defects in pancreatic development and β cell differentiation because of de-regulated Arx expression. In my study, I construct the Dnmt1 fragment, including Dnmt1 (aa.1-555), (aa.556-1103), (aa.1124-1619) and (aa.1124-1619Δ1509-1590). I prove that Dnmt1 (aa1509-1590) interact specifically with PDX1 by using GST-pull down assay. In addition, I utilized the shDnmt1 lentivirus to knockdown Dnmt1 expression in pancreatic cell line and observed the decreased expression of insulin. In the future, I will use CHIP assay to prove whether Dnmt1 will bind on the Arx promoter, and then knockdown PDX1 to observe whether the ability of Dnmt1's binding on the Arx promoter would be affected.

並列關鍵字

PDX1 ； Dnmt1 ； Pancreas development

參考文獻

Burlison, J.S., Long, Q., Fujitani, Y., Wright, C.V., and Magnuson, M.A. (2008). Pdx-1 and Ptf1a concurrently determine fate specification of pancreatic multipotent progenitor cells. Dev Biol 316, 74-86.

Christman, J.K. (2002). 5-Azacytidine and 5-aza-2'-deoxycytidine as inhibitors of DNA methylation: mechanistic studies and their implications for cancer therapy. Oncogene 21, 5483-5495.

Dhawan, S., Georgia, S., Tschen, S.I., Fan, G., and Bhushan, A. (2011). Pancreatic beta cell identity is maintained by DNA methylation-mediated repression of Arx. Dev Cell 20, 419-429.

Edlund, H. (2002). Pancreatic organogenesis--developmental mechanisms and implications for therapy. Nat Rev Genet 3, 524-532.

Gannon, M., Ables, E.T., Crawford, L., Lowe, D., Offield, M.F., Magnuson, M.A., and Wright, C.V. (2008). pdx-1 function is specifically required in embryonic beta cells to generate appropriate numbers of endocrine cell types and maintain glucose homeostasis. Dev Biol 314, 406-417.