A bacterial two-hybrid selection system for studying protein-DNA and protein-protein interactions

We have developed a bacterial "two-hybrid" system that readily allows selec tion from libraries larger than 10(8) in size. Our bacterial system may be used to study either protein-DNA or protein-protein interactions, and it of fers a number of potentially significant advantages over existing yeast-bas ed one-hybrid and two-hybrid methods. We tested our system by selecting zin c finger variants (from a large randomized library) that bind tightly and s pecifically to desired DNA target sites. Our method allows sequence-specifi c zinc fingers to be isolated in a single selection step. and thus it shoul d be more rapid than phage display strategies that typically require multip le enrichment/amplification cycles. Given the large library sizes our bacte rial-based selection system can handle, this method should provide a powerf ul tool for identifying and optimizing protein-DNA and protein-protein inte ractions.