Absolute transcript levels of thioredoxin- and glutathione-dependent redox systems in Saccharomyces cerevisiae: response to stress and modulation with growth.

We report the co-ordinated fine-tune of mRNA molecules that takes place in yeast (Saccharomyces cerevisiae) in response to diverse environmental stimuli. We performed a systematic and refined quantification of the absolute expression patterns of 16 genes coding for thioredoxin- and glutathione-dependent redox system components. Quantifications were performed to examine the response to oxidants, to sudden temperature upshifts and in association with metabolic changes accompanying culture growth and to explore the contribution of mRNA decay rates to the differences observed in basal expression levels. Collectively, these quantifications show (i) vast differences in the steady-state amounts of the investigated transcripts, cTPxI being largely overexpressed compared with GPX1 during the exponential phase and GPX2 beyond this growth stage; (ii) drastic changes in the relative abundance of the transcripts in response to oxidants and heat shock; and (iii) a unique temporal expression profile for each transcript as cells proceed from exponential to stationary growth phase, yet with some general trends such as maximal or near-maximal basal amounts of most mRNA species at early growth stages when glucose concentration is high and cells are actively growing. Moreover, the results indicate that (i) the half-lives of the investigated transcripts are longer and distributed within a narrower range than previously reported global mRNA half-lives and (ii) transcriptional initiation may play an important role in modulating the significant alterations that most mRNAs exhibit in their steady-state levels along with culture growth.