Protein interactions in the yeast two-hybrid system. Bait and prey plasmid combinations within individual yeast clones are indicated below. Sector designations correspond to those on plates. Growth of yeast on SC-L-W indicated that clones contained both the bait and prey plasmid. (A) Interaction with TBP-FL, TBP-N, and TBP-C. Sectors 1–3 show the interaction of HAP1-B155–582 with TBP-FL, TBP-C, or TBP-N, respectively. The interaction of HAP1 with TBP-FL and TBP-C, but not TBP-N resulted in growth under all conditions tested. Sectors 4–6 were auto-activation controls for TBP baits. Sectors 7–8 contained strong and weak positive interaction controls, respectively, that were supplied with the ProQuest system. The strong interaction control grew well under all conditions tested. The weak interaction control did not grow on SC-L-W-H-U, suggesting that this condition allowed growth of yeast containing only strong bait-prey interactions. Sector 9 was a negative auto-activation control showing that yeast bearing only the empty bait vector and an empty prey plasmid (no inserts) did not grow under conditions that selected for interacting bait-prey protein pairs. (B) Finer TBP deletions. Sectors 1–6 show the interaction of HAP1-A7–598 with TBP-ΔQ (sector 1) and truncated TBP-C clones (as indicated in table below; sectors 2–6). HAP1 interacted with TBP-ΔQ under all conditions tested (sector 1), but did not interact with any of the truncated TBP-C clones (sectors 2–6), suggesting that an intact TBPCORE is required for the HAP1-TBP interaction to occur. Sectors 7–12 were auto-activation controls for TBP baits, of which none were auto-active.