Hirosawa-Takamori Mitsuko, Chung Ho-Ryun, Jäckle Herbert
Max-Planck-Institut für Biophysikalische Chemie, Abteilung Molekulare Entwicklungsbiologie, Am Fassberg, D-37077 Göttingen, Germany.
EMBO Rep. 2004 Mar;5(3):317-22. doi: 10.1038/sj.embor.7400097. Epub 2004 Feb 20.
Selenoprotein synthesis is conserved from bacteria to man. It involves the differential decoding of the UGA stop codon as selenocysteine. The proteomes of both prokaryotes and eukaryotes, with the exception of yeast, contain only few selenoproteins. This low number is explained by a counterselection of readily oxidized selenocysteine after the introduction of oxygen into the atmosphere and the need to conserve selenoenzymes that control redox homeostasis of cells. Lack of selenoprotein synthesis in vertebrates impairs the oxidative stress defence and causes lethality. Here we show that Drosophila mutants that lack the translation elongation factor SelB/eEFsec fail to decode the UGA codon as selenocysteine, but they are viable and fertile. Oxidative stress responses and the lifespan of these flies are not affected. Protecting cells from oxidative stress can therefore not account for the selection pressure that conserves selenoprotein biosynthesis during the course of evolution.
从细菌到人类，硒蛋白的合成是保守的。它涉及将UGA终止密码子特异解码为硒代半胱氨酸。除酵母外，原核生物和真核生物的蛋白质组中仅含有少量硒蛋白。数量稀少的原因是大气中氧气出现后，易氧化的硒代半胱氨酸受到反向选择，以及需要保留控制细胞氧化还原稳态的硒酶。脊椎动物中硒蛋白合成的缺失会损害氧化应激防御并导致死亡。在此，我们表明，缺乏翻译延伸因子SelB/eEFsec的果蝇突变体无法将UGA密码子解码为硒代半胱氨酸，但它们能够存活且可育。这些果蝇的氧化应激反应和寿命不受影响。因此，保护细胞免受氧化应激不能解释在进化过程中保留硒蛋白生物合成的选择压力。
