A recoding element that stimulates decoding of UGA codons by Sec tRNA[Ser]Sec.
Selenocysteine insertion during decoding of eukaryotic selenoprotein mRNA requires several trans-acting factors and a cis-acting selenocysteine insertion sequence (SECIS) usually located in the 3' UTR. A second cis-acting selenocysteine codon redefinition element (SRE) has recently been described that resides near the UGA-Sec codon of selenoprotein N (SEPN1). Similar phylogenetically conserved elements can be predicted in a subset of eukaryotic selenoprotein mRNAs. Previous experimental analysis of the SEPN1 SRE revealed it to have a stimulatory effect on readthrough of the UGA-Sec codon, which was not dependent upon the presence of a SECIS element in the 3' UTR; although, as expected, readthrough efficiency was further elevated by inclusion of a SECIS. In order to examine the nature of the redefinition event stimulated by the SEPN1 SRE, we have modified an experimentally tractable in vitro translation system that recapitulates efficient selenocysteine insertion. The results presented here illustrate that the SRE element has a stimulatory effect on decoding of the UGA-Sec codon by both the methylated and unmethylated isoforms of Sec tRNA([Ser]Sec), and confirm that efficient selenocysteine insertion is dependent on the presence of a 3'-UTR SECIS. The variation in recoding elements predicted near UGA-Sec codons implies that these elements may play a differential role in determining the amount of selenoprotein produced by acting as controllers of UGA decoding efficiency.
Howard
Michael T
MT
Department of Human Genetics, University of Utah, Salt Lake City, Utah 84112, USA. mhoward@genetics.utah.edu
Moyle
Mark W
MW
Aggarwal
Gaurav
G
Carlson
Bradley A
BA
Anderson
Christine B
CB
D020413:3' Untranslated Regions; D000818:Animals; D001483:Base Sequence; D003062:Codon / Q000235:genetics* / Q000378:metabolism*; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000235:genetics; D018922:HL-60 Cells; D006801:Humans; D066298:In Vitro Techniques; D049409:Luciferases, Firefly / Q000235:genetics; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics; D012346:RNA, Transfer, Amino Acyl / Q000235:genetics* / Q000378:metabolism*; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012156:Reticulocytes / Q000378:metabolism; D017279:Selenocysteine / Q000378:metabolism; D051140:Selenoproteins / Q000235:genetics
D020413:3' Untranslated Regions; D003062:Codon; D009124:Muscle Proteins; D012346:RNA, Transfer, Amino Acyl; D011993:Recombinant Fusion Proteins; C435489:SELENON protein, human; D051140:Selenoproteins; C112705:selenocysteinyl-tRNA; D017279:Selenocysteine; D049452:Green Fluorescent Proteins; D049409:Luciferases, Firefly