Figure 2.

Schematic representation of the yeast two-hybrid screen system. This strategy is based on the fact that certain proteins regulating gene expression in yeast and other higher organisms require two functional parts—a DNA-binding domain and an activating domain—to be fully active and activate the expression of an easily detectable reporter. For this approach, a known “bait” protein is fused to the DNA-binding domain of a yeast transcription factor. The activating domain of that transcription factor is fused to test proteins from a given cell or tissue. The fused test proteins then are mixed with the fused bait. If one of the test proteins interacts with the bait, the DNA-binding and activating domains of the transcription factor are brought together and can stimulate expression of the reporter gene.