Genetic screen of the yeast environmental stress response dynamics uncovers distinct regulatory phases.

Cells respond to environmental fluctuations by regulating multiple transcriptional programs. This response can be studied by measuring the effect of environmental changes on the transcriptome or the proteome of the cell at the end of the response. However, the dynamics of the response reflect the working of the regulatory mechanisms in action. Here, we utilized a fluorescent stress reporter gene to track the dynamics of protein production in yeast responding to environmental stress. The response is modulated by changes in both the duration and rate of transcription. We probed the underlying molecular pathways controlling these two dimensions using a library of ~1,600 single- and double-mutant strains. Dissection of the effects of these mutants and the interactions between them identified distinct modulators of response duration and response rate. Using a combination of mRNA-seq and live-cell microscopy, we uncover mechanisms by which Msn2/4, Mck1, Msn5, and the cAMP/PKA pathway modulate the response of a large module of stress-induced genes in two discrete regulatory phases. Our results and analysis show that transcriptional stress response is regulated by multiple mechanisms that overlap in time and cellular location.