E. coli recA protein-directed cleavage of phage λ repressor requires polynucleotide

The recA protein mediates both genetic recombination and several cellular responses to DNA damage,including the induction of temperate bacteriophage. Induction of phage λ results from proteolytic cleavage of λ repressor directed by recA protein. We show here that this cleavage reaction requires both polynucleotide and ATP. We suggest that a stoichiometric complex of recA protein and DNA is active both to destroy repressors by proteolytic cleavage and to initiate pairing of this DNA to its homologous sequence in a DNA duplex ('strand invasion').