Using the yeast Saccharomyces cerevisiae as our experimental organism, and employing the wide range of molecular biological and molecular genetic approaches afforded by this organism, we are investigating the roles that different regulatory subunits of the protein phosphatase 2A play in qualitatively regulating the activity of this heterotrimeric enzyme, concentrating both on the requirement of this enzyme for activating stress responses as well as examining its role in properly regulating passage through the cell cycle. To a lesser extent, we are examining the role the molecular chaperone, hsp60, plays in replicating yeast mitochondrial DNA.