Affinity selection of DNA-binding proteins displayed on bacteriophage λ

Two transcription factors, human ATF1, its DNA-binding domain (ATF1BD), and the DNA-binding domain (GAL4BD) of the yeast GAL4 protein, were displayed on the surface of bacteriophage lambda vectors and efficiently selected by DNA fragments immobilized in microtiter wells, The DNA-binding proteins are fused to the carboxy terminus of the tail protein gpV and head protein gpD of the vectors, lambda foo and lambda fooDc, respectively. After a single round of affinity selection, the fusion phages were successfully enriched 60- to 4,000-fold over the vector phages, Further, the GAL4BD fusion phages were enriched 5- and 15-fold by affinity selection using specific DNA as probes over nonspecific DNA when expressed on lambda fooDc and lambda foo, respectively. The ATF1BD fusion phages were also sequence-specifically enriched greater than 4-fold when displayed on lambda foo. These results suggest that the lambda foo display system is useful for in vitro studying of protein- DNA interactions and may be applied to screening of DNA-binding protein from complex cDNA libraries through DNA-binding affinity.