10779/crick.12732839.v1 Melisa Guven Melisa Guven Reto Brem Reto Brem Peter Macpherson Peter Macpherson Matthew Peacock Matthew Peacock Peter Karran Peter Karran Oxidative damage to RPA limits the nucleotide excision repair capacity of human cells The Francis Crick Institute 2020 Cells, Cultured DNA Damage DNA Repair DNA-Binding Proteins Enzyme-Linked Immunosorbent Assay Humans Immunoblotting Oxidation-Reduction Oxidative Stress Photosensitivity Disorders Photosensitizing Agents Replication Protein A Skin Neoplasms Thioguanine Ultraviolet Rays Karran CS-ack 1103 Clinical Sciences 1112 Oncology and Carcinogenesis Dermatology & Venereal Diseases 2020-07-29 13:21:46 Journal contribution https://crick.figshare.com/articles/journal_contribution/Oxidative_damage_to_RPA_limits_the_nucleotide_excision_repair_capacity_of_human_cells/12732839 Nucleotide excision repair (NER) protects against sunlight-induced skin cancer. Defective NER is associated with photosensitivity and a high skin cancer incidence. Some clinical treatments that cause photosensitivity can also increase skin cancer risk. Among these, the immunosuppressant azathioprine and the fluoroquinolone antibiotics ciprofloxacin and ofloxacin interact with UVA radiation to generate reactive oxygen species that diminish NER capacity by causing protein damage. The replication protein A (RPA) DNA-binding protein has a pivotal role in DNA metabolism and is an essential component of NER. The relationship between protein oxidation and NER inhibition was investigated in cultured human cells expressing different levels of RPA. We show here that RPA is limiting for NER and that oxidative damage to RPA compromises NER capability. Our findings reveal that cellular RPA is surprisingly vulnerable to oxidation, and we identify oxidized forms of RPA that are associated with impaired NER. The vulnerability of NER to inhibition by oxidation provides a connection between cutaneous photosensitivity, protein damage, and increased skin cancer risk. Our findings emphasize that damage to DNA repair proteins, as well as to DNA itself, is likely to be an important contributor to skin cancer risk.