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, lambdafoo and lambdafooDc, 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 lambdafooDc and lambdafoo, respectively. The ATF1BD fusion phages were also sequence-specifically enriched greater than 4-fold when displayed on lambdafoo. These results suggest that the lambdafoo 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.