Zinc is an essential micronutrient that is abundantly utilized inside eukaryotic cells, but despite the relative importance of zinc, very little is known about how eukaryotic organisms properly metabolize this ion. S. cerevisiae will be used as a model organism to study the genetics of zinc metabolism, since the entire genome of this organism has been sequenced. Also a zinc dependent transcriptional activator (ZAP1) has been identified in this organism that is responsible for regulating genes in zinc homeostasis. The purpose of this study will be to use genome wide analysis to define a ZAP1 regulon. To accomplish this task, DNA microarray technology will be used that allows for the determination of comparative expression levels of the entire yeast genome under different conditions, such as high and low zinc concentrations. Preliminary microarray experiments revealed that over 200 genes have significantly altered transcription levels under zinc deficiency. The general design of this proposal is to repeat and refine these studies to obtain more reliable data as well as to identify genes that are truly ZAP1 regulated rather than simply sensitive to the secondary effects of zinc deficiency. Once ZAP1 target genes have been identified several of the most interesting will be selected for further genetic study by independent conformation of the zinc responsiveness then by deletional analysis of said genes to determine their function.