Santos, M.A.S and Keith, G. and Tuite, M.F. (1993) Nonstandard translational events in candida-albicans mediated by an unusual seryl-transfer rna with a 5'-cag-3' (leucine) anticodon. Embo Journal, 12 (2). pp. 607-616. ISSN 0261-4189.
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From in vitro translation studies we have previously demonstrated the existence of an apparent efficient UAG (amber) suppressor tRNA in the dimorphic fungus Candida albicans (Santos et al., 1990). Using an in vitro assay for termination codon readthrough the tRNA responsible was purified to homogeneity from C.albicans cells. The determined sequence of the purified tRNA predicts a 5'-CAG-3' anticodon that should decode the leucine codon CUG and not the UAG termination codon as originally hypothesized. However, the tRNA(CAG) sequence shows greater nucleotide homology with seryl-tRNAs from the closely related yeast Saccharomyces cerevisiae than with leucyl-tRNAs from the same species. In vitro tRNA-charging studies demonstrated that the purified tRNA(CAG) is charged with Ser. The gene encoding the tRNA was cloned from C.albicans by a PCR-based strategy and DNA sequence analysis confirmed both the structure of the tRNA(CAG) and the absence of any introns in the tRNA gene. The copy number of the tRNA(CAG) gene (1-2 genes per haploid genome) is in agreement with the relatively low abundance (< 0.5% total tRNA) of this tRNA. In vitro translation studies revealed that the purified tRNA(CAG) could induce apparent translational bypass of all three termination codons. However, peptide mapping of in vitro translation products demonstrated that the tRNA(CAG) induces translational misreading in the amino-terminal region of two RNA templates employed, namely the rabbit alpha- and beta-globin mRNAs. These results suggest that the C.albicans tRNA(CAG) is not an 'omnipotent' suppressor tRNA but rather may mediate a novel non-standard translational event in vitro during the translation of the CUG codon. The possible nature of this non-standard translation event is discussed in the context of both the unusual structural features of the tRNA(CAG) and its in vitro behaviour.
|Uncontrolled keywords:||candida-albicans; misreading; protein synthesis; transfer rna identity|
|Subjects:||Q Science > QP Physiology (Living systems) > QP517 Biochemistry
Q Science > QP Physiology (Living systems) > QP506 Molecular biology
|Divisions:||Faculties > Science Technology and Medical Studies > School of Biosciences|
|Depositing User:||O.O. Odanye|
|Date Deposited:||25 Jul 2009 01:32|
|Last Modified:||13 Mar 2012 09:44|
|Resource URI:||http://kar.kent.ac.uk/id/eprint/20657 (The current URI for this page, for reference purposes)|
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