Compartmentalization of metabolic activities is a fundamental property of eucaryotic cells. The goal of this research is to identify the genetic and biochemical elements responsible for maintaining the integrity of one subcellular compartment, the mitochondrion, and for coordinating its metabolic activities with intermediary metabolism. Novel genetic screens have identified genes in the yeast Saccharomyces cerevisiae whose products are involved in these processes. Specifically, we will: 1) Isolate and characterize genes necessary for establishing and maintaining the compartmental integrity of mitochondria. A nuclear gene localized in mitochondria of yeast will spontaneously migrate from mitochondria to the nucleus. Recessive mutations that increase the rate of DNA escape from mitochondria have been isolated. Some of these mutations affect only the rate of DNA escape while others also exhibit the genetically linked phenotype of temperature sensitive respiration. The genes identified by these mutations will be cloned and characterized in order to determine their role in maintenance of mitochondrial integrity. 2. Isolate and characterize the genetic determinants of metabolic signals that integrate mitochondrial and cytoplasmic activities. Mutations that cause incorrect signaling of the metabolic competece of mitochondria have been isolated. Mitochondria with impaired respiratory capacity normally arrest growth in G-O when presented with a nonfermentable carbon source; this class of mutations does not. These mutations potentially affect the first steps of signal transduction, before a starvation signal generated by the Ras/cAMP pathway is sent. The genes identified by these mutations will be cloned and characterized. Together, these genetic and molecular analyses will identify components important for mitochondrial compartmentalization and communication with other cellular components.
