A SECIS binding protein (SBP) is distinct from selenocysteyl-tRNA protecting factor (SePF)

详细信息    查看全文

• 作者：Fujiwara ; Toshinobu ; Busch ; Kristina ; Gross ; Hans J. ; Mizutani ; Takaharu
• 关键词：selenocysteine ; UGA codon ; SECIS RNA ; Sec-tRNA^Sec protecting factor ; SECIS binding protein ; Sec ; selenocysteine ; SECIS ; Sec insertion sequence ; SBP ; SECIS binding protein ; SePF ; Sec-tRNA protecting factor ; GPx ; glutathione peroxidase ; UTR ; untr
• 刊名：Biochimie
• 出版年：1999
• 出版时间：March, 1999
• 年：1999
• 卷：81
• 期：3
• 页码：213-218
• 全文大小：331 K

文摘

In mammals, most of the selenium contained in their body is present as an unusual amino acid, selenocysteine (Sec), whose codon is UGA. Because the UGA codon is normally recognized as a translational stop signal, it is intriguing how cells recognize and distinguish the UGA Sec codon from the UGA stop codon. In eukaryotic selenoprotein mRNAs, it has been proposed that a conserved stem-loop structure designated Sec insertion sequence (SECIS) located in the 3`-untranslated regions is required for recognition of UGA as a Sec codon. Although some proteins (SBPs) have been reported to bind to SECIS, it is not clear how the SECIS element can mediate Sec insertion at UGA. Eukaryotic Sec-tRNA^Sec is not recognized by elongation factor EF-1α, but is recognized specifically by a Sec-tRNA^Sec protecting factor, SePF, in bovine liver extracts. In this study, we provide evidence that SePF is distinct from SBP by chromatography. Upon UV irradiation, the SECIS RNA was cross-linked to a 47.5 kDa protein, a likely candidate of SBP, that is contained in the complex with a molecular mass of 150 kDa. These results suggest that SBP and SePF play different roles for the Sec incorporation. To our knowledge, this is the first demonstration that SBP is discriminated from the factor which directly recognizes Sec-tRNA^Sec, providing a novel clue to the mechanism of selenocysteine decoding in eukaryotes.