Transfer RNA structural change is a key element in the reassignment of the CUG codon in Candida albicans

Santos, Manuel and Perreau, Victoria M. and Tuite, Mick F. (1996) Transfer RNA structural change is a key element in the reassignment of the CUG codon in Candida albicans. Embo Journal, 15 (18). pp. 5060-5068. ISSN 0261-4189. (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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The human pathogenic yeast Candida albicans and a number of other Candida species translate the standard leucine CUG codon as serine, This is the latest addition to an increasing number of alterations to the standard genetic code which invalidate the theory that the code is frozen and universal. The unexpected finding that some organisms evolved alternative genetic codes raises two important questions: how have these alternative codes evolved and what evolutionary advantages could they create to allow for their selection? To address these questions in the context of serine CUG translation in C.albicans, we have searched for unique structural features in seryl-tRNA(CAG), which translates the leucine CUG codon as serine, and attempted to reconstruct the early stages of this genetic code switch in the closely related yeast species Saccharomyces cerevisiae. We show that a purine at position 33 (G(33)) in the C.albicans Ser-tRNA(CAG) anticodon loop, which replaces a conserved pyrimidine found in all other tRNAs, is a key structural element in the reassignment of the CUG codon from leucine to serine in that it decreases the decoding efficiency of the tRNA, thereby allowing cells to survive low level serine CUG translation. Expression of this tRNA in S.cerevisiae induces the stress response which allows cells to acquire thermotolerance. We argue that acquisition of thermotolerance may represent a positive selection for this genetic code change by allowing yeasts to adapt to sudden changes in environmental conditions and therefore colonize new ecological niches.

Item Type: Article
Uncontrolled keywords: Candida albicans; evolution; genetic code; serine CUG decoding; tRNA structure and function
Subjects: Q Science > QP Physiology (Living systems) > QP517 Biochemistry
Divisions: Faculties > Science Technology and Medical Studies > School of Biosciences
Depositing User: P. Ogbuji
Date Deposited: 27 May 2009 16:28
Last Modified: 10 Jun 2014 12:49
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