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Nucleotide excision repair of melphalan monoadducts
D F Grant1, T Bessho, J T Reardon
1Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205-7199, USA. grantdavidf@exchange.uams.edu
Abstract:
The nucleotide-excision repair (NER) system removes bulky DNA adducts and is thought to be involved in resistance to chemotherapeutic drugs, which act by damaging DNA. In this study, we have investigated the ability of the NER system to recognize and excise melphalan monoadducts from a 140-mer DNA substrate. We show that rodent and human cell-free extracts (CFEs) excise 26-29-nt-long oligomers from a synthetic 140-mer containing centrally located melphalan adducts. CFEs from cell lines with mutations in xeroderma pigmentosum group F or G genes did not excise these alkylated oligomers; however, mixing the two CFEs restored excision activity to the level found with wild-type CFEs. These results demonstrate the ability of the NER system to excise melphalan monoadducts, and are consistent with the hypothesis that NER may be involved in resistance to melphalan chemotherapy.
Insights
The DNA repair system, nucleotide-excision repair (NER), can remove melphalan DNA adducts. This finding supports the role of NER in melphalan chemotherapy resistance.
Area of Science:
- Molecular Biology
- Genetics
- Cancer Research
Background:
- The nucleotide-excision repair (NER) system is crucial for removing bulky DNA adducts.
- NER is implicated in cellular resistance to DNA-damaging chemotherapeutic agents.
Purpose of the Study:
- To investigate the capacity of the NER system to recognize and excise melphalan monoadducts from DNA.
- To explore the potential involvement of NER in melphalan chemotherapy resistance.
Main Methods:
- Utilized rodent and human cell-free extracts (CFEs).
- Assessed the excision of melphalan adducts from a synthetic 140-mer DNA substrate.
- Employed CFEs from cell lines deficient in xeroderma pigmentosum group F or G genes.
Main Results:
- Rodent and human CFEs successfully excised 26-29-nucleotide oligomers containing melphalan adducts.
- CFEs from xeroderma pigmentosum group F or G deficient cell lines showed impaired excision.
- Complementation of deficient CFEs with wild-type extracts restored excision activity.
Conclusions:
- The NER system demonstrates the ability to excise melphalan monoadducts from DNA.
- These findings support the hypothesis that NER contributes to resistance against melphalan chemotherapy.