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Recoding elements located adjacent to a subset of eukaryal selenocysteine-specifying UGA codons.
Michael T Howard1, Gaurav Aggarwal, Christine B Anderson
1Department of Human Genetics, University of Utah, Salt Lake City, UT 84112, USA. mhoward@genetics.utah.edu
The EMBO Journal
|March 26, 2005
Summary
Researchers discovered a new RNA element that helps insert the 21st amino acid, selenocysteine (tRNA-Sec), into proteins by re-reading UGA stop codons. This finding enhances our understanding of selenoprotein synthesis regulation.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Selenocysteine (tRNA-Sec) is the 21st amino acid, incorporated via UGA codon redefinition.
- In eukaryotes and archaea, selenocysteine insertion relies on a selenocysteine insertion sequence (SECIS) in the 3' untranslated region (3'UTR).
Purpose of the Study:
- To investigate a novel RNA element involved in selenocysteine insertion adjacent to the UGA codon in the SEPN1 gene.
- To determine the functional significance of this element in translational redefinition.
Main Methods:
- Comparative sequence analysis of eukaryal genes.
- Experimental validation using directed mutagenesis in human cells.
- Phylogenetic analysis of sequence context.
Main Results:
- A second stop codon redefinition element, distinct from the 3'UTR SECIS, was identified adjacent to the SEPN1 UGA codon.
- This element alone stimulated 6% translational redefinition of the SEPN1 UGA codon.
- In the presence of the SEPN1 3'UTR SECIS, readthrough increased to 12%.
- Phylogenetic analysis and mutagenesis confirmed the importance of a stem-loop structure 3' of the UGA codon.
Conclusions:
- A novel RNA element adjacent to the UGA codon plays a crucial role in selenocysteine insertion.
- This element, often forming a stem-loop structure, contributes significantly to translational redefinition, enhancing selenoprotein synthesis.
- Similar RNA structures may be present in other selenoprotein genes, suggesting a broader regulatory mechanism.