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Implication of p53 in base excision DNA repair: in vivo evidence
Young R Seo1, Melissa L Fishel, Sally Amundson
1Indiana University Cancer Center, Department of Microbiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
Abstract:
The tumor suppressor p53 plays an important role in response to DNA damage, including DNA repair. One DNA repair pathway, nucleotide excision repair (NER), has been well-documented to be regulated by p53. It seemed probable that p53 may affect other DNA repair pathways. We employed matched isogenic pairs of cell lines, wild-type or p53-deficient, to investigate this question using methyl methanesulfonate (MMS), a base-damaging agent. Alkylation damage induced by MMS is repaired exclusively by the base excision repair (BER) pathway. Cells carrying mutant or no p53 genes exhibited slow BER of MMS-induced DNA damage, and exhibited MMS-sensitivity. One contributing factor is the abundance of DNA polymerase beta (beta-pol), an enzyme required for BER, which was almost absent in p53 mutant and p53-null cells. Our findings demonstrate an in vivo requirement for p53 in regulating the base excision repair response, a novel finding of great potential importance in understanding the DNA repair branch of the p53 pathway.
Insights
The tumor suppressor p53 is crucial for DNA repair. This study reveals p53 regulates base excision repair (BER), essential for fixing DNA damage from agents like methyl methanesulfonate (MMS).
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The tumor suppressor p53 is a key regulator of cellular responses to DNA damage.
- While p53's role in nucleotide excision repair (NER) is established, its influence on other DNA repair pathways remains less understood.
Purpose of the Study:
- To investigate the role of p53 in the base excision repair (BER) pathway.
- To determine if p53 influences the cell's response to DNA alkylation damage.
Main Methods:
- Utilized matched isogenic cell lines with wild-type or p53-deficient genotypes.
- Exposed cells to methyl methanesulfonate (MMS), a base-damaging agent, to assess BER efficiency.
- Quantified the abundance of DNA polymerase beta (beta-pol) in different cell lines.
Main Results:
- p53-deficient cells showed impaired base excision repair (BER) of MMS-induced DNA damage.
- Cells lacking functional p53 exhibited increased sensitivity to MMS.
- The enzyme DNA polymerase beta (beta-pol), critical for BER, was significantly reduced in p53-deficient cells.
Conclusions:
- p53 is required in vivo for the regulation of the base excision repair (BER) pathway.
- This finding highlights a novel role for p53 in DNA repair, expanding our understanding of the p53 pathway's DNA repair functions.