Identification of interacting proteins using the yeast two-hybrid screen

Transmembrane-signaling events are mediated and regulated by protein-protein interactions. The yeast two-hybrid screen has proven to be an effective approach for studying interaction between signaling molecules, such as ras and raf. This approach can be used to identify new binding partners for a protein of interest or define the interaction domains and relative affinity between two proteins known to interact. To determine interaction, one protein is produced as a fusion protein with a known DNA-binding domain and a second protein is produced as a fusion protein with an acidic activation in yeast. If there is interaction between the two proteins of interest, the DNA-binding domain is brought into the vicinity of the acidic-activation domain, which recreates a functional transcriptional activator, which drives transcription of reporter genes allowing for selection and/or quantification of interaction between the two proteins. Here we describe a two-hybrid yeast system that has been used to successfully characterize protein interactions among signaling molecules.