Siebel C W, Guthrie C
Department of Biochemistry and Biophysics, University of California, San Francisco 94143-0448, USA.
Proc Natl Acad Sci U S A. 1996 Nov 26;93(24):13641-6. doi: 10.1073/pnas.93.24.13641.
Arginine methylation is a prevalent modification found in many RNA binding proteins, yet little is known about its functional consequences. Using a monoclonal antibody, 1E4, we have shown that the yeast NPL3 gene product Np13p, an essential RNA binding protein with repeated RGG motifs, is arginine-methylated in vivo. The 1E4 epitope can be generated by incubating recombinant Np13p with partially purified bovine arginine methyltransferase block this reaction. Np13p methylation requires S-adenosyl-L-methionine and also occurs in yeast extracts. An Np13p deletion mutant lacking the RGG domain is not a substrate for methylation, suggesting that the methylation sites lie within the RGG motifs. The discovery of arginine methylation in a genetically tractable organism provides a powerful entrée to understanding the function of this modification, particularly in view of the many roles postulated for Np13p in RNA processing and transport. The recent discovery of phosphorylated serine residues within the RGG domain suggests a hypothesis in which a molecular switch governed by methylation and phosphorylation regulates the biochemical properties of the Np13p RGG domain.
精氨酸甲基化是在许多RNA结合蛋白中普遍存在的一种修饰，但对其功能后果却知之甚少。利用单克隆抗体1E4，我们发现酵母NPL3基因产物Np13p，一种具有重复RGG基序的必需RNA结合蛋白，在体内被精氨酸甲基化。通过将重组Np13p与部分纯化的牛精氨酸甲基转移酶孵育可以产生1E4表位，该甲基转移酶可阻断此反应。Np13p甲基化需要S-腺苷-L-甲硫氨酸，并且也发生在酵母提取物中。缺乏RGG结构域的Np13p缺失突变体不是甲基化的底物，这表明甲基化位点位于RGG基序内。在一种遗传上易于处理的生物体中发现精氨酸甲基化，为理解这种修饰的功能提供了一个有力的切入点，特别是考虑到Np13p在RNA加工和运输中所假定的许多作用。最近在RGG结构域内发现磷酸化的丝氨酸残基，提示了一种假说，即由甲基化和磷酸化控制的分子开关调节Np13p RGG结构域的生化特性。
