Monitoring the Activation of Stress-Activated Protein Kinases Using GAL4 Fusion Transactivators

A multicellular organism is composed of many types of cells performing specialized functions. Cells have to communicate with each other for the organism to function as a whole. They do so at many levels and by various mechanisms. A cell’s identity is determined by the proteins synthesized within it. Therefore, the regulation of gene expression, especially at the transcriptional level, is a key mechanism of controlling cell growth and differentiation. To control transcription in response to extracellular stimuli originating either from other cells or the surrounding environment, signals from outside the cell are transmitted to the transcription machinery inside the nucleus via a variety of signaling molecules. These include receptors, adaptor proteins, G-proteins, protein kinases, and protein phosphatases, which form intricate networks known as signal transduction pathways (1 –4 ).