Keronninn Moreno de Lima Bessa

From DNA Repair Lab

Ultraviolet light (UV) generates DNA lesions, cyclobutante pyrimidine dimers (CPDs) and 6-4 pyrimidine-pyrimidone photoproducts being the most frequent ones. These DNA lesions can be removed from the genome by two different DNA repair processes: photoreactivation and nucleotide excision repair (NER). Photoreactivation envolves enzymes named photolyases, which contain chromophores that capture blue photons and use them to repair the UV photoproducts. Interestingly, these enzymes present a high specificity to the target lesion, being classified as CPD-photolyases and 6-4PP-photolyases. Even though photoreactivation has been found widespread in the nature, these enzymes are absent in placental mammals, including humans. In these organisms, repair of UV-induced DNA lesions is performed by NER. Our research work is interested in investigating the effects of CPDs and 6-4PPs on the induction of cellular responses upon UV irradiation. For this purpose, we have constructed adenoviral vectors carrying the marsupial CPD-photolyase and plant 6-4PP-photolyase. By employing these vectors, we have been able to demonstrate that both CPDs and 6-4PPs play important roles in cell death pathways in NER-deficient human fibroblasts, while CPDs are the major signals that lead NER-proficient human cells to death. At this time, we have been employing these recombinant adenoviral vectors for studying the effects of CPDs and 6-4PPs in cellular processes such as DNA replication and RNA transcription, which are inhibited by UV irradiation.