Damage inducibility of E. coli DNA photolase

E. coli DNA photolyase is a flavoprotein that catalyzes light dependent (300-500nm) repair of pyrimidine dimers occurring in UV irradiated DNA. Many E. coli DNA repair genes are damage inducible. These genes are regulated by the LexA repressor which binds to the SOS operators having the consensus sequence (CTG[NI0]CAG) known as the SOS box. The gene for photolyase (phr) is part of an operon consisting of orfl69-phr. Overlapping the orf169 transcriptional startsite is an SOS-box like structure (CTG[N9]CAG). By fusing the promotor region of orf169 to the carboxy terminus of a truncated lacZ gene, the authors find that expression of this fused gene is 3-10 fold higher in lexA- (deficient) cells than in lexA+ cells. The induction of the phr operon after treatment with DNA damaging agents such as mitomycin C and far UV is under investigation. In addition, the results of LexA footprinting in the region of the orf169 promotor will be presented