Metabolic tuning enables immediate adaptation to energy stress in yeast

In Saccharomyces cerevisiae, glucose depletion induces metabolic reprogramming through widespread transcriptional and translational reorganization. We report that initial very rapid translational silencing is driven by a specialized metabolic mechanism. Following glucose withdrawal, intracellular NTP levels drop drastically over 30 sec, before stabilizing at a regulated, post-stress set-point. Programmed translational control results from the differential NTP affinities of key enzymes; ATP falls below the (high) binding constants for DEAD-box helicase initiation factors, including eIF4A, driving mRNA release and blocking 80S assembly. Contrastingly, GTP levels always greatly exceed the (low) binding constants for elongation factors, allowing ribosome run-off and orderly translation shutdown. Translation initiation is immediately lost on all pre-existing mRNAs, before being selectively re-established on newly synthesized, upregulated stress-response transcripts. This response is unique to, and potentially de-risks, rapid glycolytic growth. We conclude that enzymatic constants are tuned for metabolic remodeling, allowing hierarchical inhibition of energy-consuming processes on very rapid timescales. Overall design: RNAseq samples for BY4741 Saccharomyces cerevisiae in two conditions: 1) 'Sucrose', in which cells were grown at 30° in SC medium with 2% sucrose; and 2) 'NoSucrose', in which sucrose grown cells were collected by filtration, then transferred to sucrose-free medium containing 2% each of glycerol and ethanol.