STRESS SIGNALING IN YEAST

In the yeast Saccharomyces cerevisiae three positive transcriptional c ontrol elements are activated by stress conditions: heat shock element s (HSEs), stress response elements (STREs) and AP-1 responsive element s (AREs). HSEs bind heat shock transcription factor (HSF), which is ac tivated by stress conditions causing accumulation of abnormal proteins . STREs mediate transcriptional activation by multiple stress conditio ns. They are controlled by high osmolarity via the HOG signal pathway, which comprises a MAP kinase module and a two-component system homolo gous to prokaryotic signal transducers. AREs bind the transcription fa ctor Yap1p. The three types of control elements seem to have overlappi ng, but distinct functions, Some stress proteins encoded by HSE-regula ted genes are necessary for growth of yeast under moderate stress, pro ducts of STRE-activated genes appear to be important for survival unde r severe stress and ARE-controlled genes may mainly function during ox idative stress and in the response to toxic conditions, such as caused by heavy metal ions.