Conserved motifs in the Msn2-activating domain are important for Msn2-mediated yeast stress response.

The Msn2 and Msn4 transcription factors play crucial roles in the yeast general stress response. Previous studies identified several large functional domains of Msn2, mainly through crude truncations. Here, using bioinformatics and experimental approaches to examine Msn2 structure-function relationships, we have identified new functional motifs in the Msn2 transcriptional-activating domain (TAD). Msn2 is predicted to adopt an intrinsically disordered structure with two short structural motifs in its TAD. Mutations in these motifs dramatically decreased Msn2 transcriptional activity, yeast stress survival and Msn2 nuclear localization levels. Using the split-ubiquitin assay, we found that these motifs are important for the interaction of Msn2 with Gal11, a subunit of the mediator complex. Finally, we show that one of these motifs is functionally conserved in several yeast species, highlighting a common mechanism of Msn2 transcriptional activation throughout yeast evolution.