Two-hybrid screening in yeast is a technology a number of companies are using to map protein-protein interactions, notably CuraGen Corp. (CRGN, Branford, Conn.) and Myriad Genetics Inc. (Salt Lake City, Utah). Hybrigenics S.A. believes it has a unique version of the technology.

In general, two-hybrid systems use the transcriptional machinery in yeast to detect interactions between two proteins, i.e., to produce a signal that occurs only if there is an interaction. The system starts with a "bait" protein fused to a binding domain and a "prey" protein fused to an activation domain. The binding domain and activation domain, which are normal parts of the yeast's transcription machinery, can only interact if the bait and prey proteins physically interact. If they do, the transcription machinery of the yeast is recruited and expresses a reporter gene that turns the yeast colony blue. The sequence corresponding to the prey protein then can be extracted from the colony.