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The adaptor for stress‐related selenoprotein synthesis does not require aminoacylation for its maturation
Author(s) -
Carlson Bradley A,
Xu XueMing,
Lee Byeong Jae,
Gladyshev Vadim N,
Hatfield Dolph L
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.156.2
Subject(s) - aminoacylation , transfer rna , mutant , protein biosynthesis , translation (biology) , selenocysteine , biology , gene isoform , xenopus , selenoprotein , population , signal transducing adaptor protein , microbiology and biotechnology , chemistry , biochemistry , rna , messenger rna , cysteine , glutathione , phosphorylation , gene , demography , sociology , enzyme , glutathione peroxidase
The mammalian selenocysteine (Sec) tRNA population contains two isoforms that differ by a 2′‐O‐methyl group on the ribose at position 34, designated Um34. Um34 synthesis at position 34 is dependent on the presence of selenium (Se) and the resulting Um34‐modified isoform in turn is required for expression of stress‐related selenoproteins (SRSPs). Since Se is involved in 1) Sec synthesis that occurs on its tRNA, 2) the Se donor, SPS2, a selenium‐containing protein, and 3) Um34 synthesis, a question is raised regarding the number of steps Se is required before the SRSP adaptor is generated, i.e., must this isoform be aminoacylated before the final methylation event? If so, then Se is required at multiple steps for Um34 synthesis. To address this question, we mutated the discriminator base at position 73 (G73‐>A73) that prevents aminoacylation of Sec tRNA, or the 3′terminal base (A76‐>G76) that is aminoacylated poorly, and compared the rate of synthesis of Um34 following microinjection into Xenopus oocytes of wild type and mutant Sec tRNAs. Um34 was synthesized on each tRNA, but interestingly, the mutant isoforms appeared to add Um34 faster. Thus, the adaptor for SRSPs expression can mature independent of its aminoacylation status.