Interplay between termination and translation machinery in eukaryotic selenoprotein synthesis
Interplay between termination and translation machinery in eukaryotic selenoprotein synthesis
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DOI：
10.1006/jmbi.2001.4809
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发表时间：
2001-07-20
影响因子：
5.6
通讯作者：
Berry, MJ
中科院分区：
文献类型：
--
作者：
Grundner-Culemann, E;Martin, GW;Berry, MJ
真核生物中翻译的终止由终止密码子识别因子eRF1和eRF3催化，eRF3是eRF1和核糖体依赖性GT3。在硒蛋白mRNA中，通常指定终止的UGA密码子作为有义密码子发挥替代功能。硒代半胱氨酸的掺入涉及一个独特的tRNA与UGA互补的反密码子，一个独特的延伸因子，这种tRNA的特异性，顺式作用的二级结构硒蛋白mRNA，称为SECIS元件。为了深入了解硒代半胱氨酸插入和终止机制之间的相互作用，我们研究了过表达eRF1和eRF3以及改变UGA密码子上下文对瞬时转染系统中硒蛋白合成效率的影响。eRF1的过表达不增加天然存在的硒代半胱氨酸密码子的终止。令人惊讶的是，硒代半胱氨酸掺入增强。eRF3的过表达不影响掺入效率。两种因子的共表达再现了单独使用eRF 1的效果。最后，我们表明，核苷酸上下文立即上游和下游的UGA密码子显着影响终止掺入比和响应eRF过表达。硒代半胱氨酸的掺入和终止的机制的影响进行了讨论。(C)北京：科学出版社.
Termination of translation in eukaryotes is catalyzed by eRF1, the stop codon recognition factor, and eRF3, an eRF1 and ribosome-dependent GTPase. In selenoprotein mRNAs, UGA codons, which typically specify termination, serve an alternate function as sense codons. Selenocysteine incorporation involves a unique tRNA with an anticodon complementary to UGA, a unique elongation factor specific for this tRNA, and cis-acting secondary structures in selenoprotein mRNAs, termed SECIS elements. To gain insight into the interplay between the selenocysteine insertion and termination machinery, we investigated the effects of overexpressing eRF1 and eRF3, and of altering UGA codon context, on the efficiency of selenoprotein synthesis in a transient transfection system. Overexpression of eRF1 does not increase termination at naturally occurring selenocysteine codons. Surprisingly, selenocysteine incorporation is enhanced. Overexpression of eRF3 did not affect incorporation efficiency. Coexpression of both factors reproduced the effects with eRF1 alone. Finally, we show that the nucleotide context immediately upstream and downstream of the UGA codon significantly affects termination to incorporation ratios and the response to eRF overexpression. Implications for the mechanisms of selenocysteine incorporation and termination are discussed. (C) 2001 Academic Press.