RESUMO
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.
Assuntos
Reparo do DNA/efeitos da radiação , Proteínas de Ligação a DNA/metabolismo , Transtornos de Fotossensibilidade/fisiopatologia , Proteína de Replicação A/efeitos da radiação , Neoplasias Cutâneas/fisiopatologia , Raios Ultravioleta/efeitos adversos , Células Cultivadas , Dano ao DNA/genética , Reparo do DNA/efeitos dos fármacos , Proteínas de Ligação a DNA/genética , Ensaio de Imunoadsorção Enzimática , Humanos , Immunoblotting , Oxirredução/efeitos dos fármacos , Oxirredução/efeitos da radiação , Estresse Oxidativo , Transtornos de Fotossensibilidade/etiologia , Fármacos Fotossensibilizantes/efeitos adversos , Fármacos Fotossensibilizantes/farmacologia , Proteína de Replicação A/efeitos dos fármacos , Proteína de Replicação A/metabolismo , Neoplasias Cutâneas/etiologia , Tioguanina/metabolismoRESUMO
In the present study, the protein microarray was used to investigate the protein expression in human B-cell lymphoblastoid cells intermittently exposed to 1.8-GHz GSM radiofrequency radiation (RFR) at the specific absorption rate (SAR) of 2.0 W/kg for 24 h. The differential expression of 27 proteins was found, which were related to DNA damage repair, apoptosis, oncogenesis, cell cycle and proliferation (ratio >1.5-fold, P<0.05). The results validated with Western blot assay indicated that the expression of RPA32 was significantly down-regulated (P<0.05) while the expression of p73 was significantly up-regulated in RFR exposure group (P<0.05). Because of the crucial roles of those proteins in DNA repair and cell apoptosis, the results of present investigation may explain the biological effects of RFR on DNA damage/repair and cell apoptosis.
