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Base excision repair is efficient in cells lacking poly(ADP-ribose) polymerase 1.
M D Vodenicharov1, F R Sallmann, M S Satoh
1Poly(ADP-ribose) Metabolism Group and DNA Repair Group, Health and Environment Unit, Laval University Medical Research Center, CHUQ and Faculty of Medicine, Laval University, 2705 Boulevard Laurier, Ste-Foy, Quebec G1V 4G2, Canada.
Nucleic Acids Research
|October 12, 2000
Summary
Cells lacking Poly(ADP-ribose) polymerase 1 (PARP-1) can repair DNA damage normally. Their hypersensitivity to radiation and alkylating agents is linked to reduced poly(ADP-ribose) formation, not a DNA repair defect.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Poly(ADP-ribose) polymerase 1 (PARP-1) is a nuclear enzyme crucial for DNA damage response.
- PARP-1 deficient mice and cells show increased sensitivity to ionizing radiation and alkylating agents.
- The role of PARP-1 in base excision repair (BER) and its contribution to DNA damage sensitivity remain unclear.
Purpose of the Study:
- To investigate base excision repair (BER) capacity in PARP-1 deficient cells.
- To determine if impaired BER underlies the hypersensitivity of PARP-1 null mutant cells to DNA damaging agents.
- To elucidate the precise mechanism behind PARP-1's role in cellular response to DNA damage.
Main Methods:
- In vitro DNA repair assays using cell extracts from wild-type and PARP-1 deficient cells.
- Plasmid DNA repair assessment after damage induction by X-rays (single-strand breaks) or N-methyl-N'-nitro-N-nitrosoguanidine (methylated bases).
- In vivo genomic DNA repair analysis in PARP-1 deficient cells treated with N-methyl-N'-nitro-N-nitrosoguanidine.
Main Results:
- Cell extracts from both wild-type and PARP-1 deficient cells exhibited similar DNA repair efficiencies for X-ray induced single-strand breaks.
- Both cell types demonstrated comparable repair of methylated bases in plasmid DNA.
- PARP-1 deficient cells repaired genomic DNA as efficiently as wild-type cells following treatment with N-methyl-N'-nitro-N-nitrosoguanidine.
Conclusions:
- PARP-1 deficient cells possess a normal capacity for repairing single-strand DNA breaks and repairing modified bases during BER.
- The hypersensitivity of PARP-1 null mutant cells to gamma-irradiation and alkylating agents is not due to a defect in DNA repair itself.
- This hypersensitivity likely results from significantly diminished poly(ADP-ribose) formation during BER in the absence of PARP-1.