THE YEAST TRIBRID SYSTEM - GENETIC DETECTION OF TRANS-PHOSPHORYLATED ITAM-SH2-INTERACTIONS

Protein-protein interactions are often dependent on the post-translati onal modification of one component of a complex. To facilitate the stu dy of these interactions in signal transduction, we have developed the yeast tribrid system, a modification of the yeast two-hybrid system. We demonstrate that the interactions are dependent upon the presence o f a tyrosine kinase, an SH2 domain and a tyrosine containing substrate . Using the gamma subunit of the high-affinity IgE receptor, Fc epsilo n RI, this approach has been used to isolate a novel SH2-containing fa mily member. The mRNA encoding this novel protein is differentially ex pressed in rat tissues. The yeast tribrid system can be readily adapte d for the characterization of novel tyrosine kinases or substrates, as well as the study of protein-protein interactions which involve other post-translational modifications.