Unique and redundant roles for HOG MAPK pathway components as revealed by whole-genome expression analysis.
The Saccharomyces cerevisiae high osmolarity glycerol (HOG) mitogen-activated protein kinase pathway is required for osmoadaptation and contains two branches that activate a mitogen-activated protein kinase (Hog1) via a mitogen-activated protein kinase kinase (Pbs2). We have characterized the roles of common pathway components (Hog1 and Pbs2) and components in the two upstream branches (Ste11, Sho1, and Ssk1) in response to elevated osmolarity by using whole-genome expression profiling. Several new features of the HOG pathway were revealed. First, Hog1 functions during gene induction and repression, cross talk inhibition, and in governing the regulatory period. Second, the phenotypes of pbs2 and hog1 mutants are identical, indicating that the sole role of Pbs2 is to activate Hog1. Third, the existence of genes whose induction is dependent on Hog1 and Pbs2 but not on Ste11 and Ssk1 suggests that there are additional inputs into Pbs2 under our inducing conditions. Fourth, the two upstream pathway branches are not redundant: the Sln1-Ssk1 branch has a much more prominent role than the Sho1-Ste11 branch for activation of Pbs2 by modest osmolarity. Finally, the general stress response pathway and both branches of the HOG pathway all function at high osmolarity. These studies demonstrate that cells respond to increased osmolarity by using different signal transduction machinery under different conditions.
O'Rourke
Sean M
SM
Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, California 94143-0448, USA. seanor@molbio.uoregon.edu
Herskowitz
Ira
I
D020869:Gene Expression Profiling; D020930:MAP Kinase Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000235:genetics* / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009997:Osmotic Pressure; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics* / Q000502:physiology
D008565:Membrane Proteins; C459787:SHO1 protein, S cerevisiae; C087199:SSK1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C088589:HOG1 protein, S cerevisiae; D020928:Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C067018:Ste11 protein, S cerevisiae; D020929:Mitogen-Activated Protein Kinase Kinases; C089356:PBS2 protein, S cerevisiae