In both Prokaryotes and Eukaryotes, a major adaptive response to various Stress conditions is to change the repertoire of Gene expression. Prokaryotic cells commonly employ the two-component Signal Transduction Systems, where a “sensor” Histidine Kinase, often located in the Plasmamembrane, mediates environmental signals to a cytoplasmic “response regulator” that controls transcription of the target gene. Although Homologous mechanisms have been found also in some Eukaryotic organisms, recent studies have uncovered a pivotal role of MAPK (Mitogen-Activated Protein Kinase) Cascades in stress signaling of Yeast and Vertebrate cells. Each MAPK Cascade comprises a series of three or more protein kinases, each phosphorylating and thereby activating the next in line. The last Kinase of the series (the MAPK) is activated by dual [...]