Photolyase/Cryptochrome Family Blue-light Photoreceptors Use Light Energy to Repair DNA or Set the Circadian Clock

Photoreactivation is the reversal of the effects of far-UV (200–300 nm) on organisms by simultaneous or subsequent exposure to near-UV blue-light (300–500 nm).Far-UV produces cyclobutane pyrimidine dimers(Pyr<>Pyr) and pyrimidine-pyrimidone (6-4) photoproducts (Pyr [6-4] Pyr) in DNA. These lesions inhibit replication and transcription, induce mutation, and causegrowth arrest and cell death. Photolyases are enzymesthat use the energy of blue light to reverse the UV photoproduct to normal bases and thus photoreactivate the organism to health...