Genetics lecture 21 notes analyzing the code from genome to phenome. Defining the interactome (protein-protein) two hybrid assay: Separate the activities of the gal4 protein. One component contains gal4 binding domain and other contains gal4 activation domain. Create a fusion protein that expresses a protein that consists of the binding domain. When proteins don"t interact gal 4 binding domain bound to cis acting element & no activation of reporter gene. When proteins interact binding domain in close proximity to activation domain they can activate expression of reporter. Have one budding yeast strain expressing the dna binding domain to your first protein of interest b for bait. Have another haploid strain of opposite type expressing activation domain fusing to second protein of interest. Mix 2 cells together forms a diploid (induced mating) where diploid strain is expressing both fusion proteins. If 2 proteins don"t interact, then reporter is off.