Pulse-Width Modulation of Gene Expression in Budding Yeast

Metabolic oscillations are characterized by alternating phases of high and low respiratory activity, associated with transcription of genes involved in biosynthetic pathways and growth, and in catabolism and stress response. However, the functional consequences of transcriptome oscillations remain unclear, since most proteins are too stable to be affected by oscillatory transcript abundances. In this work, we investigate a transcriptome time series during an unstable state of the oscillation. Our analyses confirm previous suggestions that the relative times spent in the alternative transcription states are coupled to growth rate. This pulse-width modulation of transcription provides a simple mechanism for the long-standing question of how cells adjust their ribosome content and growth rate to environmental conditions. A mathematical model of this idea reproduces both the almost linear relation of transcript and protein abundances and the non-linear relation of oscillation periods to growth rate.