Recoding elements located adjacent to a subset of eukaryal selenocysteine-specifying UGA codons.
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.
Howard
Michael T
MT
Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA. mhoward@genetics.utah.edu
Aggarwal
Gaurav
G
Anderson
Christine B
CB
Khatri
Shikha
S
Flanigan
Kevin M
KM
Atkins
John F
JF
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003062:Codon; D005057:Eukaryotic Cells; D017930:Genes, Reporter; D006801:Humans; D008969:Molecular Sequence Data; D009124:Muscle Proteins / Q000235:genetics; D009690:Nucleic Acid Conformation; D012313:RNA / Q000737:chemistry / Q000235:genetics; D017279:Selenocysteine / Q000235:genetics* / Q000378:metabolism; D051140:Selenoproteins; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA
D003062:Codon; D009124:Muscle Proteins; C435489:SELENON protein, human; C495235:SELENOT protein, human; D051140:Selenoproteins; D017279:Selenocysteine; D012313:RNA