Funções duplas de códons no código genético

quinta-feira, julho 29, 2010

Dual functions of codons in the genetic code

Critical Reviews in Biochemistry and Molecular Biology
August 2010, Vol. 45, No. 4 , Pages 257-265

Alexey V. Lobanov1, Anton A. Turanov1, Dolph L. Hatfield2, Vadim N. Gladyshev1

1Division of Genetics, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, USA

2Molecular Biology of Selenium Section, Laboratory of Cancer Prevention, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA

Address for Correspondence:Vadim N. Gladyshev, Division of Genetics, Brigham and Women’s Hospital and Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115, USA.

The discovery of the genetic code provided one of the basic foundations of modern molecular biology. Most organisms use the same genetic language, but there are also well-documented variations representing codon reassignments within specific groups of organisms (such as ciliates and yeast) or organelles (such as plastids and mitochondria). In addition, duality in codon function is known in the use of AUG in translation initiation and methionine insertion into internal protein positions as well as in the case of selenocysteine and pyrrolysine insertion (encoded by UGA and UAG, respectively) in competition with translation termination. Ambiguous meaning of CUG in coding for serine and leucine is also known. However, a recent study revealed that codons in any position within the open reading frame can serve a dual function and that a change in codon meaning can be achieved by availability of a specific type of RNA stem-loop structure in the 3′-untranslated region. Thus, duality of codon function is a more widely used feature of the genetic code than previously known, and this observation raises the possibility that additional recoding events and additional novel features have evolved in the genetic code.


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