The Trichoderma reesei Cry1 Protein Is a Member of the Cryptochrome/Photolyase Family with 6–4 Photoproduct Repair Activity

DNA-photolyases use UV-visible light to repair DNA damage caused by UV radiation. The two major types of DNA damage are cyclobutane pyrimidine dimers (CPD) and 6-4 photoproducts (6-4PP), which are repaired under illumination by CPD and 6-4 photolyases, respectively. Cryptochromes are proteins related to DNA photolyases with strongly reduced or lost DNA repair activity, and have been shown to function as blue-light photoreceptors and to play important roles in circadian rhythms in plants and animals. Both photolyases and cryptochromes belong to the cryptochrome/photolyase family, and are widely distributed in all organisms. Here we describe the characterization of cry1, a member of the cryptochrome/photolyase protein family of the filamentous fungus Trichoderma reesei. We determined that cry1 transcript accumulates when the fungus is exposed to light, and that such accumulation depends on the photoreceptor Blr1 and is modulated by Envoy. Conidia of cry1 mutants show decreased photorepair capacity of DNA damage caused by UV light. In contrast, strains over-expressing Cry1 show increased repair, as compared to the parental strain even in the dark. These observations suggest that Cry1 may be stimulating other systems involved in DNA repair, such as the nucleotide excision repair system. We show that Cry1, heterologously expressed and purified from E. coli, is capable of binding to undamaged and 6-4PP damaged DNA. Photorepair assays in vitro clearly show that Cry1 repairs 6-4PP, but not CPD and Dewar DNA lesions.