Genetic code supports targeted insertion of two amino acids by one codon
Anton A Turanov1, Alexey V Lobanov, Dmitri E Fomenko
1Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA.
Science (New York, N.Y.)
|January 10, 2009
Summary
The genetic code may assign two amino acids to a single codon. Messenger RNA (mRNA) structure and codon location determine whether UGA codes for selenocysteine or cysteine.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The genetic code traditionally follows a strict one-to-one mapping between codons and amino acids.
- This presumed universality is fundamental to our understanding of protein synthesis.
Purpose of the Study:
- To investigate whether a single codon can indeed code for multiple amino acids.
- To explore the mechanisms governing such dual-function codons within messenger RNA (mRNA).
Main Methods:
- Analysis of the ciliate Euplotes crassus genetic system.
- Investigating the role of 3' untranslated region (UTR) structure in codon function.
- Expressing Euplotes mRNA constructs in mammalian cells to assess conserved function.
Main Results:
- The codon UGA was found to specify both selenocysteine and cysteine in Euplotes crassus.
- This dual-functionality of the UGA codon was observed within the same gene.
- Euplotes mRNA structural elements maintained the location-dependent dual function of UGA when expressed in mammalian cells.
Conclusions:
- The genetic code is more flexible than previously assumed, allowing one codon to specify multiple amino acids.
- Specific mRNA structures and codon context dictate the amino acid incorporated, challenging the strict codon-amino acid correspondence.
- Findings suggest a broader regulatory capacity within the genetic code, applicable across different biological systems.
