Oxidative Damage to RPA Limits the Nucleotide Excision Repair Capacity of Human Cells

J Invest Dermatol. 2015 Nov;135(11):2834-2841. doi: 10.1038/jid.2015.255. Epub 2015 Jul 2.

Abstract

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cells, Cultured
  • DNA Damage / genetics
  • DNA Repair / drug effects
  • DNA Repair / radiation effects*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Immunoblotting
  • Oxidation-Reduction / drug effects
  • Oxidation-Reduction / radiation effects
  • Oxidative Stress
  • Photosensitivity Disorders / etiology
  • Photosensitivity Disorders / physiopathology*
  • Photosensitizing Agents / adverse effects
  • Photosensitizing Agents / pharmacology
  • Replication Protein A / drug effects
  • Replication Protein A / metabolism
  • Replication Protein A / radiation effects*
  • Skin Neoplasms / etiology
  • Skin Neoplasms / physiopathology*
  • Thioguanine / metabolism
  • Ultraviolet Rays / adverse effects*

Substances

  • DNA-Binding Proteins
  • Photosensitizing Agents
  • Replication Protein A
  • Thioguanine