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Science 9 January 2009:
Vol. 323. no. 5911, pp. 259 - 261
DOI: 10.1126/science.1164748
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Reports

Genetic Code Supports Targeted Insertion of Two Amino Acids by One Codon

Anton A. Turanov,1* Alexey V. Lobanov,1* Dmitri E. Fomenko,1 Hilary G. Morrison,2 Mitchell L. Sogin,2 Lawrence A. Klobutcher,3 Dolph L. Hatfield,4 Vadim N. Gladyshev1{dagger}

Strict one-to-one correspondence between codons and amino acids is thought to be an essential feature of the genetic code. However, we report that one codon can code for two different amino acids with the choice of the inserted amino acid determined by a specific 3' untranslated region structure and location of the dual-function codon within the messenger RNA (mRNA). We found that the codon UGA specifies insertion of selenocysteine and cysteine in the ciliate Euplotes crassus, that the dual use of this codon can occur even within the same gene, and that the structural arrangements of Euplotes mRNA preserve location-dependent dual function of UGA when expressed in mammalian cells. Thus, the genetic code supports the use of one codon to code for multiple amino acids.

1 Department of Biochemistry and Redox Biology Center, University of Nebraska, Lincoln, NE 68588, USA.
2 Josephine Bay Paul Center, Marine Biological Laboratory, Woods Hole, MA 02543, USA.
3 Department of Molecular, Microbial and Structural Biology, University of Connecticut Health Center, Farmington, CT 06032, USA.
4 Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.

* These authors contributed equally to this work.

{dagger} To whom correspondence should be addressed. E-mail: vgladyshev1{at}unl.edu

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Science. ISSN 0036-8075 (print), 1095-9203 (online)