Recoding elements located adjacent to a subset of eukaryal selenocysteine-specifying UGA codons
Recoding elements located adjacent to a subset of eukaryal selenocysteine-specifying UGA codons
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DOI：
10.1038/sj.emboj.7600642
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发表时间：
2005-04-20
期刊：
影响因子：
11.4
通讯作者：
Atkins, JF
中科院分区：
文献类型：
--
作者：
Howard, MT;Aggarwal, G;Atkins, JF
第21位氨基酸硒代半胱氨酸在蛋白质中的掺入是通过UGA密码子的动态翻译重定义在生命的所有三个领域中指定的。在真核生物和古细菌中，硒代半胱氨酸的插入需要一个顺式作用的硒代半胱氨酸插入序列（SECIS），通常位于硒蛋白mRNA的3'UTR。在这里，我们提出了比较序列分析和实验数据支持存在的第二个终止密码子重定义元件位于邻近的硒代半胱氨酸编码UGA密码子在真核基因，SEPN1。该元件足以刺激人细胞中SEPN1 UGA密码子的高水平（6%）翻译重定义。当在SEPN1 3'UTR SECIS存在下测试时，通读水平进一步增加至12%。序列背景的定向诱变和同源性强烈支持起始于UGA密码子3'的六个核苷酸的茎环的重要性。在Sps2、SelH、SelO和SelT硒蛋白基因中，能够形成强RNA结构的序列也被鉴定为3'邻近或靠近硒代半胱氨酸编码UGA密码子。
Incorporation of the 21st amino acid, selenocysteine, into proteins is specified in all three domains of life by dynamic translational redefinition of UGA codons. In eukarya and archaea, selenocysteine insertion requires a cis-acting selenocysteine insertion sequence ( SECIS) usually located in the 3'UTR of selenoprotein mRNAs. Here we present comparative sequence analysis and experimental data supporting the presence of a second stop codon redefinition element located adjacent to a selenocysteine-encoding UGA codon in the eukaryal gene, SEPN1. This element is sufficient to stimulate high-level (6%) translational redefinition of the SEPN1 UGA codon in human cells. Readthrough levels further increased to 12% when tested in the presence of the SEPN1 3'UTR SECIS. Directed mutagenesis and phylogeny of the sequence context strongly supports the importance of a stem loop starting six nucleotides 3' of the UGA codon. Sequences capable of forming strong RNA structures were also identified 3' adjacent to, or near, selenocysteine-encoding UGA codons in the Sps2, SelH, SelO, and SelT selenoprotein genes.