Natural reassignment of CUU and CUA sense codons to alanine in Ashbya mitochondria
Natural reassignment of CUU and CUA sense codons to alanine in Ashbya mitochondria
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DOI：
10.1093/nar/gkt842
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发表时间：
2014-01-01
影响因子：
14.9
通讯作者：
Lang, B. Franz
中科院分区：
文献类型：
--
作者：
Ling, Jiqiang;Daoud, Rachid;Lang, B. Franz
不同密码子重新分配事件的发现表明，规范遗传密码不是通用的。在分子水平上研究编码重新分配对于理解遗传密码进化至关重要，并为合成生物学中的遗传密码操纵提供线索。在这里，我们报告了棉豆阿什比亚（Eremothecium）线粒体中的一个新的重新分配事件，棉豆是一种与酵母（糖酵母科）相关的丝状生长植物病原体。对线粒体 DNA 编码蛋白中保守位置的生物信息学研究表明，CUU 和 CUA 密码子对应于棉麻中的丙氨酸，而不是标准密码中的亮氨酸或酵母线粒体中的苏氨酸。通过质谱法在蛋白质水平上证实了 CUA 重新分配为 Ala。我们进一步证明预测的 tRNA(UAG)(Ala) 在体内被转录和准确加工，并负责 Ala 重新分配。酶学研究表明 tRNA(UAG)(Ala) 能被棉蚜线粒体丙氨酰-tRNA 合成酶 (AgAlaRS) 有效识别。 AlaRS 通常识别 tRNA (Ala) 的 G3:U70 碱基对； Ashbya tRNA(UAG)(Ala) 中 G3A 的变化消除了 AgAlaRS 对其的识别。相反，酿酒酵母 tRNA(UAG)(Thr) 中的 A3G 突变赋予 AgAlaRS 识别 tRNA 的能力。我们的工作强调了线粒体中自然遗传密码的动态特征，以及 tRNA 身份转换的相对简单性。
The discovery of diverse codon reassignment events has demonstrated that the canonical genetic code is not universal. Studying coding reassignment at the molecular level is critical for understanding genetic code evolution, and provides clues to genetic code manipulation in synthetic biology. Here we report a novel reassignment event in the mitochondria of Ashbya (Eremothecium) gossypii, a filamentous-growing plant pathogen related to yeast (Saccharomycetaceae). Bioinformatics studies of conserved positions in mitochondrial DNA-encoded proteins suggest that CUU and CUA codons correspond to alanine in A. gossypii, instead of leucine in the standard code or threonine in yeast mitochondria. Reassignment of CUA to Ala was confirmed at the protein level by mass spectrometry. We further demonstrate that a predicted tRNA(UAG)(Ala) is transcribed and accurately processed in vivo, and is responsible for Ala reassignment. Enzymatic studies reveal that tRNA(UAG)(Ala) is efficiently recognized by A. gossypii mitochondrial alanyl-tRNA synthetase (AgAlaRS). AlaRS typically recognizes the G3:U70 base pair of tRNA(Ala); a G3A change in Ashbya tRNA(UAG)(Ala) abolishes its recognition by AgAlaRS. Conversely, an A3G mutation in Saccharomyces cerevisiae tRNA(UAG)(Thr) confers tRNA recognition by AgAlaRS. Our work highlights the dynamic feature of natural genetic codes in mitochondria, and the relative simplicity by which tRNA identity may be switched.