Coordination of events for mating in Saccharomyces cerevisiae involves arrest of the mitotic cycle in the G1 phase, transcriptional induction of relevant genes and differentiation into a mating competent form. In this process, a signal initiated by interaction of a peptide mating pheromone with a cell surface receptor stimulates an intracellular signal transduction pathway. Dr. Errede's lab is studying three genes that specify components of this signaling pathway. Two genes, STE11 and STE7, encode the prototype input and central protein kinases, respectively, of a MAPK activation cascade. The third, STE12, encodes a transcription factor necessary for induction of pheromone responsive genes. Genetic, cell biological and biochemical approaches are used with these molecules to uncover the principles that govern the assembly, specificity and integration of signaling networks in the cell.