2 The environmental stress response: a common yeast response to diverse environmental stresses

Unicellular organisms require specific internal conditions for optimal growth and function, however sudden changes in the external environment can perturb the internal milieu, disrupting normal processes. Therefore, cells must maintain their internal system despite fluctuations in the external surroundings. One mechanism that yeast cells use to protect the internal system from the effects of environmental variation is to initiate a common gene expression program that generally protects the cell during stressful times. This program, referred to as the environmental stress response, includes ~900 genes whose expression is stereotypically altered when yeast cells are shifted to stressful environments. The coordinated expression changes of these genes is a common feature of the responses to many different environments, however the regulation of these expression changes is gene-specific and condition-specific, indicating that initiation of the program is precisely controlled in response to each new environment. This review will focus on recent developments in defining and characterizing the genes that participate in the environmental stress response and the regulatory mechanisms that the cell utilizes to orchestrate this program.