a genuine system to test and screen protein interactions

The discovery of the yeast two-hybrid system in 1989 by Stanley Fields et al. has revolutionized the way protein interactions could be detected. Indeed, yeast microbiology and molecular biology tools were replacing traditional immuno-precipitation experiments and the need of antibodies.

Using plasmid expressing tools in genetically modified yeast cells, a genuine system was invented to account for the reconstitution of a functional transcription factor (TF).

Upon physical binding of protein X with protein Y, the DNA Binding Domain (DBD) of a transcriptional activator is brought in close proximity to its Activation Domain (AD) counterpart. Reconstitution of a functional TF activates the production of an auxotrophy marker (His3 commonly) which in turn allows His- yeast cells to grow on a selective medium lacking Histidine.

This system has been originally developed to test for the interaction between two known proteins . Further versions were developed to propose cDNA and genomic library screenings with researchers seeking the interacting proteins of their favorite protein in a given cell type, tissue or organism.