FIGURE 2. Yeast two-hybrid approaches.

a, The yeast two-hybrid system. DNA-binding and activation domains (circles) are fused to proteins X and Y; the interaction of X and Y leads to reporter gene expression (arrow). b, A standard two-hybrid search. Protein X, present as a DNA-binding domain hybrid, is screened against a complex library of random inserts in the activation-domain vector (square brackets). c, A two-hybrid array approach. Protein X is screened against a complete set of full-length open reading frames (ORFs) present as activation-domain hybrids (shown as yeast transformants spotted onto microtitre plates). d, A two-hybrid search using a library of full-length ORFs. The set of ORFs as activation-domain hybrids (microtitre plates in square brackets) is combined to form a low-complexity library. e, A two-hybrid pooling strategy. Pools of ORFs as both DNA-binding domain and activation-domain hybrids (square brackets) are screened against each other.