Building a new cell is a substantial metabolic commitment that requires not only energy, but also building blocks for new proteins, nucleic acids and membranes. How does a cell assess nutrient availability before it makes a growth decision? Studies of nutrient sensing and signaling pathways have revealed important roles for the PKA, TOR and AMPK pathways in conveying metabolic status to steer cells toward growth or quiescence. Recently, we discovered that the metabolite acetyl-CoA can induce histone acetylation, which consequently activates the transcriptional growth program in budding yeast. Thus, a key output of the activation of growth control pathways could be the upregulated production of acetyl-CoA.Our study made use of a continuous culture system termed the yeast metabolic cycle (YMC), where a highly synchronized cell population continuously alternates between growth and quiescent phases in each cycle of oxygen consumption (Fig. 1).
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