The budding yeast Saccharomyces cerevisiae possesses a very flexible and complex programme of gene expression when exposed to a plethora of environmental insults. Therefore, yeast cell homeostasis control is achieved through a highly coordinated mechanism of transcription regulation involving several factors, each performing specific functions. Here, we present our current knowledge of the function of the yeast activator protein family, formed by eight basic-leucine zipper trans-activators, which have been shown to play an important role in stress response.