Fine tuning of translation termination efficiency in Saccharomyces cerevisiae involves two factors in close proximity to the exit tunnel of the ribosome

¹ IGM
² University of Massachusetts

^* To whom correspondence should be addressed. E-mail: isabelle.hatin{at}igmors.u-psud.fr.

Submitted on January 11, 2007
Revised on March 5, 2007
Accepted on 27 April 2007

	Abstract

In eukaryotes, release factor 1 and 3 (eRF1 and eRF3) are recruited to promote translation termination when a stop codon on the mRNA enters at the ribosomal A-site. However, their over-expression increases only moderately termination efficiency, suggesting that other factors might be involved in the termination process. In order to determine such unknown components, we performed a genetic screen in Saccharomyces cerevisiae that identified genes increasing termination efficiency when over-expressed. For this purpose, we constructed a dedicated reporter strain in which a leaky stop codon is inserted into the chromosomal copy of the ade2 gene. Twenty-five anti-suppressor candidates were identified and characterized for their impact on readthrough. Among them, SSB1 and snR18, two factors close to the exit tunnel of the ribosome, directed the strongest anti-suppression effects when over-expressed, showing that they may be involved in fine tuning of the translation termination level.

Key Words: SSB chaperones, eEF1B, snoRNA, translation termination

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