Genome-wide analysis of gene expression regulated by the yeast cell wall integrity signalling pathway

The cell integrity pathway of Saccharomyces cerevisiae monitors cell wall r emodelling during growth and differentiation. Additionally, this pathway re sponds to environmental stresses that challenge the integrity of the cell w all. We conducted a genome-wide survey of genes whose expression was altere d in response to activation of Mpk1/Slt2, the MAP kinase, under the control of cell integrity signalling. We identified 25 genes whose regulation was altered by Mpk1 activity. Among these, 20 were positively regulated by Mpk1 , and five were negatively regulated. Most of the genes identified encode e ither known or suspected cell wall proteins or enzymes involved in cell wal l biogenesis. These include glycosyl-phosphatidylinositol (GPI) proteins, m embers of the Pir family of cell wall proteins, Mpk1 itself and others. All of the regulation detected was mediated by the Rlm1 transcription factor, a MADS-box protein that is phosphorylated and activated by Mpk1, but for wh ich no transcriptional targets had been identified. A similar pattern of re gulation was observed when cell integrity signalling was induced by environ mental stress (i.e. temperature upshift).