NEWLY IDENTIFIED STRESS-RESPONSIVE PROTEIN-KINASES, KRS-1 AND KRS-2

The activation of protein kinases is a frequent response of cells to t reatment with growth factors, chemicals, heat shock, or apoptosis-indu cing agents. However, when several agents result in the activation of the same enzymes, it is unclear how specific biological responses are generated. We describe here two protein kinases that are activated by a subset of stress conditions or apoptotic agents but are not activate d by commonly used mitogenic stimuli. Purification and cloning demonst rate that these protein kinases are members of a subfamily of kinases related to Ste20p, a serine/threonine kinase that functions early in a pheromone responsive signal transduction cascade in yeast. The specif icity of Krs-1 and Krs-2 activation and their similarity to Ste20p sug gest that they may function at an early step in phosphorylation events that are specific responses to some forms of chemical stress or extre me heat shock.