Chen Shun-Jia, Lin Grace, Chang Kuang-Jung, Yeh Lu-Shu, Wang Chien-Chia
Department of Life Science, National Central University, Jung-li, Taiwan 32001.
Department of Life Science, Tzu-Chi University, Hua-lien, Taiwan 97041.
J Biol Chem. 2008 Feb 8;283(6):3173-3180. doi: 10.1074/jbc.M706968200. Epub 2007 Dec 7.
Previous studies have shown that translation of mrna for yeast glycyl-tRNA synthetase is alternatively initiated from UUG and a downstream AUG initiation codon. Evidence presented here shows that unlike an AUG initiation codon, efficiency of this non-AUG initiation codon is significantly affected by its sequence context, in particular the nucleotides at positions -3 to -1 relative to the initiation codon. A/A/R (R represents A Or G) and C/G/C appear to be the most and least favorable sequences at these positions, respectively. Mutation of the native context sequence -3 to -1 from AAA to CGC reduced translation initiation from the UUG codon up to 32-fold and resulted in loss of mitochondrial respiration. although an AUG initiation codon is, in general, unresponsive to context changes in yeast, an AAA (-3 to -1) to CGC mutation still reduced its initiating activity up to 8-fold under similar conditions. these results suggest that sequence context is more important for translation initiation in yeast than previously appreciated.
先前的研究表明，酵母甘氨酰 - tRNA合成酶的mRNA翻译可从UUG和下游的AUG起始密码子处交替起始。本文提供的证据表明，与AUG起始密码子不同，这种非AUG起始密码子的效率受其序列上下文的显著影响，特别是相对于起始密码子的 - 3至 - 1位的核苷酸。A/A/R（R代表A或G）和C/G/C似乎分别是这些位置上最有利和最不利的序列。将天然上下文序列 - 3至 - 1从AAA突变为CGC，使从UUG密码子起始的翻译减少了32倍，并导致线粒体呼吸丧失。虽然一般来说，AUG起始密码子对酵母中的上下文变化不敏感，但在类似条件下，从AAA（ - 3至 - 1）到CGC的突变仍使其起始活性降低了8倍。这些结果表明，序列上下文对酵母中的翻译起始比以前认为的更为重要。
