Stress-activated MAP kinase (mitogen-activated protein kinase) pathways of budding and fission yeasts.

All eukaryotic cells share the ability to sense and rapidly respond to environmental stress by initiating cyto-protective programmes of gene expression, protein translation and protein degradation. The molecular basis underlying these processes is, however, not well understood. Recently, attention has become focused on an evolutionarily conserved family of protein kinases called the stress-activated mitogen-activated protein kinases (SAPKs) that are activated when cells are challenged with a variety of environmental stresses or cytotoxic agents. Two members of the SAPK family, HOG1 and Sty1/Spc1, have been identified in the distantly related budding and fission yeasts, respectively. This has allowed researchers to genetically and biochemically dissect the structure of these pathways to begin to understand how they are activated and the role of the SAPKs in the cyto-protective response. In this chapter, I compare the structure of the SAPK pathways in the two yeasts and illustrate how this knowledge may benefit our understanding of stress sensing in mammalian cells.