Inhibition of Selenoprotein Synthesis by Selenocysteine tRNA[Ser]Sec Lacking Isopentenyladenosine

Abstract

A common posttranscriptional modification of tRNA is the isopentenylation of adenosine at position 37, creating isopentenyladenosine (i(6)A). The role of this modified nucleoside in protein synthesis of higher eukaryotes is not well understood. Selenocysteyl (Sec) tRNA (tRNA([Ser]Sec)) decodes specific UGA codons and contains i(6)A. To address the role of the modified nucleoside in this tRNA, we constructed a site-specific mutation, which eliminates the site of isopentenylation, in the Xenopus tRNA([Ser]Sec) gene. Transfection of the mutant tRNA([Ser]Sec) gene resulted in 80% and 95% reduction in the expression of co-transfected selenoprotein genes encoding type I and II iodothyronine deiodinases, respectively. A similar decrease in type I deiodinase synthesis was observed when transfected cells were treated with lovastatin, an inhibitor of the biosynthesis of the isopentenyl moiety. Neither co-transfection with the mutant tRNA gene nor lovastatin treatment reduced type I deiodinase mRNA levels. Also, mutant tRNA expression did not alter initiation of translation or degradation of the type I deiodinase protein. Furthermore, isopentenylation of tRNA([Ser]Sec) was not required for synthesis of Sec on the tRNA. We conclude that isopentenylation of tRNA([Ser]Sec) is required for efficient translational decoding of UGA and synthesis of selenoproteins.

Mod5 protein binds to tRNA gene complexes and affects local transcriptional silencing

“…We tested whether the previously defined catalytic activity of Mod5 is required for tgm silencing by depleting its DMAPP substrate in two different ways (23)(24)(25). The first method was to treat cells with the drug Atorvastatin, which inhibits an early enzyme in DMAPP biosynthesis, 3-hydroxy-3-methyl-glutarylCoA (HMG-CoA) reductase (24).…”

Metabolic networks in ferroptosis (Review)

“…Furthermore, human prostate cancer PC3 cells treated with atorvastatin undergo autophagy, whereas simvastatin leads to the induction of apoptosis in HCT116 colorectal cancer cells and renal cell carcinoma cells (41). Statins also downregulate the mevalonate pathway and block the biosynthesis of cellular isoprenoids, including IPP, which are responsible for the post-translational modification of Sec-tRNA [Ser]Sec and the synthesis of GPX4 (6,35,42). Although there is no experimental evidence demonstrating the link between statins and ferroptosis, statins downregulate the mevalonate pathway, which is a crucial signaling event for GPX4 maturation.…”

A regulatory role for Sec tRNA[Ser]Sec in selenoprotein synthesis

“…To investigate the role of mcm 5 Um in UGA translation, a dominant-negative acting mutant tRNA [Ser]Sec that does not form the modified nucleotide i 6 A at position 37 (due to the in vitro mutagenesis of that position for an A to a G) and does not undergo ribose methylation at mcm 5 U34 was used (Warner et al 2000;Moustafa et al 2001 A − cells was assessed using each of the reporter constructs and shown to be greatly diminished compared to control cells (Fig. 6).…”