研究員 / 本院分生所

EDUCATION AND POSITIONS HELD:

• Ph. D. Biochemistry, University of Montana, USA (1981).
• Visiting Assistant Professor, University of Montana, USA (1981-1982)
• Postdoctoral Fellow, Institute of Enzyme Research, University of Wisconsin, Madison, Wisconsin, USA (1982-1984)
• Scientist, Pharmacia/LKB, USA (1984-1986)
• Associate Research Fellow, Institute of Molecular Biology, Academia Sinica, ROC (1986-1990)
• Visiting Professor, Department of Biological Sciences, Carnegie Mellon University, USA (2002)
• Research Fellow, Institute of Molecular Biology, Academia Sinica, ROC (1990-present)

RESEARCH INTERESTS:

The main interest of our laboratory is on proteins with arginine side chain methylation and the subsequent cellular responses. There are at least three types of protein arginine methyltransferases (PRMTs). The type I enzymes mediate the formation of ω-N^G-monomethylarginine (ωMMA) and asymmetric ω-N^G-N^G-dimethylarginine (aDMA). The type II enzymes have the symmetric ω-N^G-N^G'-dimethylarginine (sDMA) in addition to the ωMMA as products. The δ-guanidino nitrogen of the arginine side chain can also be methylated with a type IV PRMT from the yeast. Asymmetrical dimethylation of arginines has been shown to influence mRNA nuclear export, protein-protein interactions and transcription. Symmetrical dimethylarginine methylation is required for the localization of SMN (survival of motor neurons) in Cajal bodies and pre-mRNA splicing. Proteins with monomethyl arginine have been observed in tumor cells during apoptosis. The cellular functions of proteins with monomethylarginine are at present unknown.
Our laboratory is using yeast as a model system to study the cellular responses to protein arginine methylation. We have identified Sbp1p as a substrate of Hmt1p which is a type I PRMT. Sbp1p is a nucleolar single-strand nucleic acid binding protein that we found associated with the ribosome. Sbp1p interacts with numerous proteins but only the methylated Sbp1p can bind Nop13p, Mas1p and Rpl16Ap. The results implicate the involvement of methylated Sbp1p in rRNA processing.
Ribosomal protein Rpl12p is δ-monomethylated at Arg67 by RMT2. Yeast strain with RPL12A and RPL12B double deletion exhibits slow growth and slow translation. Cells transformed with plasmids encoding the wild type Rpl12p or its Arg67 to lysine mutant have different growth rate. We are testing whether mRNAs are preferentially translated on the polysomes of these strains.

本實驗室的研究重心主要在蛋白質精氨酸支鏈的甲基化及其後續之細胞反應。PRMTs 至少有三種類型，第一型酵素是形成ω-NG-單甲基精氨酸及非對稱ω-NG-NG-雙甲基精氨酸。第二型酵素產物除了ω-NG-單甲基精氨酸外還有對稱ω-NG-NG,- 雙甲基精氨酸。而酵母菌第四型PRMT 則是將精氨酸支鏈的δ-鳥糞嘌呤氮予以甲基化。證據顯示精氨酸之非對稱雙甲基化會影響mRNA 自細胞核的輸出，蛋白質-蛋白質間的互相作用及轉錄作用。對稱雙甲基精氨酸之甲基化與Cajal bodies 內SMN(運動神經元之存活) 的定位及pre-mRNA 的接合有關。在凋亡之腫瘤細胞內曾發現具有單甲基精氨酸的蛋白質。目前並不了解具δ-單甲基精氨酸之蛋白質的細胞功能。
本實驗室以酵母菌為模型系統對精氨酸甲基轉移酶之細胞功能進行研究。已確認Sbp1p 為酵母菌第一型精氨酸甲基轉移酶Hmt1p 的受質。Sbp1p是依個核仁內結合單股核酸之蛋白, 我們發現它與核醣體結合。 Sbp1p和許多蛋白質互相作用但是只有甲基化的Sbp1p 能和 Nop3p, Mas1p, 及 Rpl16p 結合。 此結果顯示甲基化之 Sbp1p 參與了 rRNA 之後續處裡。
核醣蛋白 Rpl12p 是被RMT2在精氨酸67 δ-單甲基化。 將 RPL12A及 RPL12B兩個基因均剔除之酵母菌顯現較慢的生長及轉譯速度。 將帶有原始型或精氨酸67以離氨酸取代之突變型基因的質體轉型進入酵母菌細胞會使其有不同的生長速度。 我們正在測試是否有些mRNA在這些菌種的核醣體上被優先轉譯。