STRESS CAUSES INDUCTION OF MAP KINASE-SPECIFIC PHOSPHATASE AND RAPID REPRESSION OF MAP KINASE-ACTIVITY IN DROSOPHILA

Heat shock and chemical stress induce activation of heat shock (stress) genes and synthesis of heat shock proteins. It is not yet fully understood which molecular mechanism leads to activation. Probably denatured proteins play an important role in activating the transcription factor (HSF), but on the other hand there are many hints that a phosphorylation event is involved, too. During a search for a possible signal transduction system in Drosophila Schneider 2 cells we analysed the response of the mitogen-activated protein (MAP) kinase after stress and its regulation by phosphatases. We show here that stress activates a MAP kinase-specific phosphatase in Drosophila and inhibits MAP kinase activity.