Research ArticleStress responses

Cells alter their tRNA abundance to selectively regulate protein synthesis during stress conditions

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Sci. Signal.  04 Sep 2018:
Vol. 11, Issue 546, eaat6409
DOI: 10.1126/scisignal.aat6409

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The right proteins at the right time

Cells must tailor protein synthesis so that proteins that enable growth and proliferation and those that enable adaptation under stressful conditions are produced at the appropriate times. Torrent et al. (see also the Focus by Pechmann) noted that yeast genes encoding proteins involved in growth and proliferation used common codons, whereas those encoding stress response proteins tended to use rare codons. Furthermore, the authors found that stress skewed the tRNA pool toward those tRNAs that recognized rare codons and that stress proteins were translated faster than those involved in growth and proliferation. Thus, codon usage and adjustments to the tRNA pool serve as an important layer of regulation to ensure that cells produce proteins appropriate to the conditions that they are experiencing.

Abstract

Decoding the information in mRNA during protein synthesis relies on tRNA adaptors, the abundance of which can affect the decoding rate and translation efficiency. To determine whether cells alter tRNA abundance to selectively regulate protein expression, we quantified changes in the abundance of individual tRNAs at different time points in response to diverse stress conditions in Saccharomyces cerevisiae. We found that the tRNA pool was dynamic and rearranged in a manner that facilitated selective translation of stress-related transcripts. Through genomic analysis of multiple data sets, stochastic simulations, and experiments with designed sequences of proteins with identical amino acids but altered codon usage, we showed that changes in tRNA abundance affected protein expression independently of factors such as mRNA abundance. We suggest that cells alter their tRNA abundance to selectively affect the translation rates of specific transcripts to increase the amounts of required proteins under diverse stress conditions.

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