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Updated: Jul 3, 2026
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Proofreading and DNA Repair Assay Using Single Nucleotide Extension and MALDI-TOF Mass Spectrometry Analysis
Published on: June 19, 2018
Long patch base excision repair in mammalian mitochondrial genomes
Bartosz Szczesny1, Anne W Tann, Matthew J Longley
1Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, USA.
The Journal of Biological Chemistry
|July 19, 2008
Summary
Mitochondria utilize long-patch base excision repair (LP-BER) for DNA damage, involving a novel 5'-exo/endonuclease and DNA polymerase gamma. This pathway repairs oxidized deoxyribose fragments, distinct from nuclear repair mechanisms.
Area of Science:
- Mitochondrial biology
- DNA repair mechanisms
- Molecular genetics
Background:
- Mitochondrial DNA (mtDNA) is vulnerable to reactive oxygen species (ROS)-induced damage.
- Base excision repair (BER) repairs nuclear and mitochondrial DNA lesions.
- Single nucleotide BER (SN-BER) repairs oxidized bases and abasic sites using 1-nucleotide incorporation.
Purpose of the Study:
- To investigate the presence and function of long-patch BER (LP-BER) in mitochondria.
- To identify the enzymes involved in mitochondrial LP-BER.
- To elucidate the mechanism of repairing lyase-resistant AP sites in mitochondria.
Main Methods:
- Analysis of mitochondrial extracts from mouse and human cells.
- Assay for 5 eal-exo/endonuclease activity in mitochondrial extracts.
- Investigation of LP-BER activity in FEN-1-depleted mitochondrial extracts.
- Immunocomplex isolation and analysis of APE1-containing complexes.
Main Results:
- Mitochondrial extracts possess 5 eal-exo/endonuclease activity crucial for repairing lyase-resistant AP site analogs.
- LP-BER in mitochondria involves multinucleotide incorporation.
- A novel 5 eal-exo/endonuclease, distinct from FEN-1, appears to mediate mitochondrial LP-BER.
- Mitochondrial LP-BER requires DNA polymerase gamma and its 3 eal-exonuclease activity.
Conclusions:
- Long-patch base excision repair (LP-BER) occurs in mitochondria.
- Mitochondrial LP-BER utilizes a unique 5 eal-exo/endonuclease and DNA polymerase gamma.
- This pathway is essential for repairing complex DNA lesions within mitochondria.
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