The objective of this work is to elucidate the role of tRNA in cellular regulatory mechanisms and to determine the function of the many minor, non-vital tRNA species which have been observed. We intend to identify and characterize as many genes as possible which affect tRNA structure. These genes will include both tRNA structural genes and genes involved in the maturation or modification of tRNA. We will determine the effects on cellular physiology that result from destruction or alteration of these genes. In addition, several gene regulatory mechanisms including that for histidine biosynthesis and for proline degradation will be investigated in hopes of demonstrating the role of tRNA.