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Characterization of defective nucleotide excision repair in XPC mutant mice
D L Cheo1, H J Ruven, L B Meira
1Department of Pathology, The University of Texas Southwestern Medical Center, Dallas 75235, USA.
Abstract:
Nucleotide excision repair (NER) is a fundamental process required for maintaining the integrity of the genome in cells exposed to environmental DNA damage. Humans defective in NER suffer from the hereditary cancer-prone disease xeroderma pigmentosum. In order to model this disease in mice a mutation in the mouse XPC gene was generated and used to replace a wild-type XPC allele in mouse embryonic stem cells by homologous recombination. These cells were used to derive XPC mutant mice. Fibroblasts from mutant embryos were more sensitive to the cytotoxic effects of ultraviolet light than wild-type and heterozygous cells. Repair synthesis of DNA following irradiation with ultraviolet light was reduced in these cells, indicating a defect in NER. Additionally, XPC mutant embryo fibroblasts were specifically defective in the removal of pyrimidine (6-4) pyrimidone photoproducts from the non-transcribed strand of the transcriptionally active p53 gene. Mice defective in the XPC gene appear to be an excellent model for studying the role of NER and its interaction with other proteins in the molecular pathogenesis of cancer in mammals following exposure to environmental carcinogens.
Insights
Researchers created XPC mutant mice to model xeroderma pigmentosum, a cancer predisposition disease caused by defective nucleotide excision repair (NER). These mice exhibit reduced DNA repair and increased sensitivity to UV light, offering a valuable model for cancer research.
Area of Science:
- Genetics
- Molecular Biology
- Cancer Research
Background:
- Nucleotide excision repair (NER) maintains genome integrity against environmental DNA damage.
- Defects in NER cause xeroderma pigmentosum, a hereditary cancer-prone disease in humans.
Purpose of the Study:
- To create a mouse model for xeroderma pigmentosum by generating a mutation in the XPC gene.
- To investigate the role of XPC in DNA repair and its implications for cancer pathogenesis.
Main Methods:
- Homologous recombination was used to introduce a mutation into the mouse XPC gene in embryonic stem cells.
- XPC mutant mice were derived from these modified cells.
- Fibroblast sensitivity to ultraviolet light and DNA repair synthesis were assessed.
Main Results:
- XPC mutant fibroblasts showed increased sensitivity to ultraviolet light cytotoxicity compared to wild-type and heterozygous cells.
- A significant reduction in DNA repair synthesis was observed in XPC mutant cells post-irradiation.
- These cells demonstrated a specific defect in removing pyrimidine (6-4) photoproducts from the p53 gene.
Conclusions:
- Mice with XPC gene defects serve as a robust model for studying nucleotide excision repair (NER).
- This model is valuable for understanding the molecular mechanisms of cancer development related to DNA damage and repair pathways.