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Negative interference of metal (II) ions with nucleotide excision repair in human cell-free extracts
1Institut de Pharmacologie et Biologie Structurale, UPR 9062, CNRS, Toulouse, France.
Abstract:
Inhibition of the nucleotide excision repair (NER) process is believed to cause the potentiation of the genotoxic and mutagenic effects of DNA damaging agents like UV-light or cisplatin by metal ions. However, the precise underlying molecular mechanism of this phenomenon is still unknown. Using in vitro assays, we have determined the potential interference of several metal (II) ions with the lesion recognition and strand incision/displacement steps of the NER mechanism, independently from the DNA polymerization step. When combinations of an optimal Mg2+ concentration and concentrations of various metal ions in a range from 0.1 to 1 mM were tested, all combinations, with Mn2+ and Ni2+ excepted, inhibited specifically the incision repair activity by human protein extracts. There was a good correlation for Cd2+, Co2+, Fe2+, Cu2+, Hg2+, Pb2+ and Zn2+ between an inhibiting effect on the incision activity and a reduced protein binding activity to a damaged DNA probe as assessed by gel mobility shift assay.
Insights
Metal ions can inhibit nucleotide excision repair (NER), a key DNA repair process. This study found that several metal ions, including cadmium and lead, specifically block the incision step in NER, potentially increasing DNA damage effects.
Area of Science:
- Molecular Biology
- Biochemistry
- Toxicology
Background:
- Nucleotide excision repair (NER) is crucial for removing DNA damage caused by agents like UV light and cisplatin.
- Metal ions are suspected to potentiate genotoxic effects by interfering with NER, but the mechanism remains unclear.
Purpose of the Study:
- To investigate the molecular mechanisms by which metal (II) ions interfere with the NER pathway.
- To determine if metal ions affect lesion recognition or strand incision steps of NER.
Main Methods:
- In vitro assays were used to assess the impact of various metal (II) ions on NER.
- Gel mobility shift assays evaluated protein binding to damaged DNA probes.
Main Results:
- Most tested metal ions (Cd2+, Co2+, Fe2+, Cu2+, Hg2+, Pb2+, Zn2+) inhibited the incision activity of human protein extracts in NER.
- Mn2+ and Ni2+ did not show significant inhibition.
- A correlation was observed between inhibition of incision activity and reduced DNA binding affinity for several metal ions.
Conclusions:
- Specific metal ions can inhibit critical steps of the NER pathway, particularly the incision activity.
- This inhibition may contribute to the potentiation of genotoxic and mutagenic effects observed with DNA damaging agents in the presence of these metal ions.