探討PRMT5甲基化HURP的機轉及其在細胞中的生理意義

The mechanisms and cellular significances of PRMT5-induced HURP methylation

郭奕群(Yi-Chun Kuo)

指導教授 ： 余長澤

國立暨南國際大學/科技學院/應用化學系/碩士(2015年)

https://doi.org/10.6837/NCNU.2015.00258

摘要

蛋白質是生物體內實際執行生理功能的分子，在細胞中蛋白質常進行多種後轉譯修飾作用 (Posttranslational modification)，以賦予蛋白質更多的功能。例如後轉譯修飾可以調節蛋白質在細胞內的位置、蛋白質與蛋白質間的交互作用、蛋白質的活性與穩定度等。在眾多蛋白修飾中，甲基化的研究起步較晚，但其牽涉的生化反應十分廣泛，因此蛋白質甲基化的細胞功能近年來陸續受到重視。
我們實驗室的研究與相關文獻指出，PRMT5 (Protein aRginine MethylTransferase 5) 為一高度表現在數種癌症組織的蛋白質甲基轉移酶，具有促進細胞轉型的活性；PRMT5會甲基化同樣具致細胞轉型活性的HURP (Hepatoma UpRegulated Protein)，此發現促使我們想要了解PRMT5甲基化HURP的機轉及甲基化HURP在細胞中的生理意義。在機轉方面，PRMT5透過支架蛋白 (scaffold protein) Ajuba與蛋白質激酶 (protein kinase) Aurora-A交互作用，進而使PRMT5與Aurora-A可以相互調節彼此的活性；之後， Ajuba與PRMT5協助因子RioK1會幫助PRMT5辨識下游受質HURP，並甲基化HURP於Arg 122的位置。另一方面，本論文也發現去蛋白質甲基酶JMJD6可以去甲基化HURP。細胞的生理意義方面，HURP 122甲基化會促進由Aurora-A所催化於HURP Ser 627的磷酸化，繼而使得HURP蛋白質穩定度提升。此外，HURP 122甲基化會決定HURP在細胞內的分布；例如在細胞分裂期，Arg 122的甲基化會讓HURP遠離紡錘絲與著絲點的交界，HURP因之無法穩定此區域的紡錘絲，使得染色體排列異常。另一方面，HURP 122的甲基化促使高基氏體過於穩定，使高基氏體不易進行碎裂移位重組(polarized assembly)，因而阻礙細胞的爬行；反之，無法甲基化的HURP則能大幅度促進細胞移行。總之，本論文首度揭露PRMT5甲基化HURP的機制與後續的細胞反應，對於解開此PRMT5/HURP訊息途徑的細胞功能做了重要的初步貢獻。

關鍵字

甲基化 ； PRMT5 ； HURP ； Ajuba

並列摘要

Proteins are molecules of practical implementation of physiological functions , the protein is usually carried out in a variety of cells, post-translational modification (Posttranslational modification), to give the protein more function, E.g., post-translational modification may adjust the position of the protein in the cell, protein-protein interactions, protein activity and stability, etc. Among the many protein modification, the methylation of a late start, but the biochemical reaction which involves very extensive, and therefore protein methylation cell function in recent years have taken seriously.
Our laboratory research and related literature, PRMT5 (Protein aRginine MethylTransferase 5) is a highly expression in several types of cancer tissue protein methyl transferase, promote cell transformation activity. PRMT5 be the same with the methylation-induced cell transformation activity HURP (Hepatoma UpRegulated Protein), this finding promoted us want to know PRMT5-HURP methylation mechanisms and HURP physiological significance in cells. In mechanisms, PRMT5 through scaffold protein-Ajuba with protein kinase-Aurora-A interaction, thereby PRMT5 and Aurora-A can adjust each other's activity. Afterward Ajuba and RioK1 will assist PRMT5 identify downstream HURP, then methylate HURP in Arg 122. On the other hand, this paper also found that protein demethylation enzymes JMJD6 can go demethylation HURP. In cellular significances, HURP 122 promotes methylation catalyzed by Aurora-A in HURP Ser 627 phosphorylation, which in turn makes HURP enhance the stability of the protein. Furthermore, HURP 122 methylation decided HURP distributed in cells. For example, in cell division, Arg 122 methylation make HURP spindle fibers away from the junction with the centromere, HURP consequent spindle can not be stabilized in this region silk, making chromosome misalignment. On the other hand, HURP 122 methylated Golgi is promote to stable, so that the Golgi is not easy to polarized assembly, and thus hinder the cell migration. Conversely, demethylated HURP is promote cell migration. In summary, this study for the first time reveal the mechanisms and cellular significances of PRMT5-induced HURP methylationsubsequent methylation, for the PRMT5/HURP signal pathway made important initial contribution.

並列關鍵字

Methylation ； PRMT5 ； HURP ； Ajuba

參考文獻

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