1. What is the advantage to having target gene expression be inducible? Since the activator proteins in the DupLEX-Aś system are not Gal4p-based, the galactose-inducible Gal4 promoter can be used to drive expression of the target protein. This allows potentially toxic target proteins to be obtained since cells can be grown with glucose as the carbon source to prevent expression of the target protein until needed. 2. How can I be sure that my cloned interactor is not just a false positive? Unfortunately, a clone cannot be called "real" until the biological relevance for the interaction can be established. Nevertheless, the DupLEX-Aś system includes some features that can help you decide whether or not a particular clone is worth pursuing further. For example, two "negative" bait proteins are included to make sure a potential interaction is specific for the bait used in the screen. Also, the B42 domain is fused in-frame to a hemagglutinin tag (HA tag), allowing co-immunoprecipitation testing of the interactors to be performed using commercially available HA tag antibodies and antibodies to the bait protein being screened (if they exist). 3. What if my bait autoactivates in the Gal4 system? Unlike the Gal4-based systems, the DupLEX-Aś system contains reporters of varying sensitivities. If your protein does not activate reporter gene expression on its own, then you should use the most sensitive reporters when performing the screen. However, if your protein does autoactivate reporter gene expression, then one of the less sensitive reporters may allow you to perform the screen anyway. Six reporters (three LEU2 and three lacZ) are included which can be tested before screening to determine which is the best one to use for your particular protein.