Aström S U, Byström A S
Department of Microbiology, University of Umeå, Sweden.
Cell. 1994 Nov 4;79(3):535-46. doi: 10.1016/0092-8674(94)90262-3.
Using a genetic screen in yeast aimed at identifying cellular factors involved in initiator and elongator methionine tRNA discrimination in the translational process, we have identified a mutation that abolish the requirement for elongator methionine tRNA. The gene affected, which we call the ribosylation of the initiator tRNA gene or RIT1, encodes a 2'-O-ribosyl phosphate transferase. This enzyme modifies exclusively the initiator tRNA in position 64 using 5'-phosphoribosyl-1'-pyrophosphate as the modification donor. As the initiator tRNA participates both in the initiation and elongation of translation in a rit1 strain, we conclude that the 2'-O-ribosyl phosphate modification discriminates the initiator tRNAs from the elongator tRNAs during protein synthesis. The modification enzyme was shown to recognize the stem-loop IV region that is unique in eukaryotic cytoplasmic initiator tRNAs.
通过在酵母中进行遗传筛选，旨在识别翻译过程中参与起始甲硫氨酸tRNA和延伸甲硫氨酸tRNA识别的细胞因子，我们鉴定出了一种突变，该突变消除了对延伸甲硫氨酸tRNA的需求。受影响的基因，我们称之为起始tRNA核糖基化基因或RIT1，编码一种2'-O-核糖基磷酸转移酶。该酶仅使用5'-磷酸核糖-1'-焦磷酸作为修饰供体，对64位的起始tRNA进行修饰。由于起始tRNA在rit1菌株中既参与翻译起始又参与延伸，我们得出结论，2'-O-核糖基磷酸修饰在蛋白质合成过程中区分起始tRNA和延伸tRNA。已证明该修饰酶识别真核细胞质起始tRNA中独特的茎环IV区域。
