Related Experiment Video
Updated: Nov 20, 2025
Simultaneous Mapping and Quantitation of Ribonucleotides in Human Mitochondrial DNA
Published on: November 14, 2017
Poly(ADP-ribose) polymerase 1 regulates mitochondrial DNA repair in an NAD-dependent manner
Geoffrey K Herrmann1, William K Russell2, Nisha J Garg3
1Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, Texas, USA; Sealy Center for Structural Biology, University of Texas Medical Branch, Galveston, Texas, USA.
Abstract:
Mitochondrial DNA is located in organelle that house essential metabolic reactions and contains high reactive oxygen species. Therefore, mitochondrial DNA suffers more oxidative damage than its nuclear counterpart. Formation of a repair enzyme complex is beneficial to DNA repair. Recent studies have shown that mitochondrial DNA polymerase (Pol γ) and poly(ADP-ribose) polymerase 1 (PARP1) were found in the same complex along with other mitochondrial DNA repair enzymes, and mitochondrial PARP1 level is correlated with mtDNA integrity. However, the molecular basis for the functional connection between Pol γ and PARP1 has not yet been elucidated because cellular functions of PARP1 in DNA repair are intertwined with metabolism via NAD+ (nicotinamide adenosine dinucleotide), the substrate of PARP1, and a metabolic cofactor. To dissect the direct effect of PARP1 on mtDNA from the secondary perturbation of metabolism, we report here biochemical studies that recapitulated Pol γ PARylation observed in cells and showed that PARP1 regulates Pol γ activity during DNA repair in a metabolic cofactor NAD+ (nicotinamide adenosine dinucleotide)-dependent manner. In the absence of NAD+, PARP1 completely inhibits Pol γ, while increasing NAD+ levels to a physiological concentration that enables Pol γ to resume maximum repair activity. Because cellular NAD+ levels are linked to metabolism and to ATP production via oxidative phosphorylation, our results suggest that mtDNA damage repair is coupled to cellular metabolic state and the integrity of the respiratory chain.
Insights
Poly(ADP-ribose) polymerase 1 (PARP1) regulates mitochondrial DNA polymerase (Pol γ) activity. This regulation is dependent on nicotinamide adenine dinucleotide (NAD+), linking DNA repair to cellular metabolism.
Area of Science:
- Mitochondrial biology
- DNA repair mechanisms
- Biochemistry
Background:
- Mitochondrial DNA (mtDNA) is susceptible to oxidative damage due to its location and high reactive oxygen species production.
- Mitochondrial DNA polymerase (Pol γ) and poly(ADP-ribose) polymerase 1 (PARP1) are part of a DNA repair complex, with PARP1 levels correlating with mtDNA integrity.
- The precise molecular link between PARP1 and Pol γ in mtDNA repair, considering PARP1's metabolic ties via NAD+, remains unclear.
Purpose of the Study:
- To biochemically investigate the direct interaction and functional relationship between PARP1 and Pol γ in mtDNA repair.
- To elucidate the role of the metabolic cofactor nicotinamide adenine dinucleotide (NAD+) in PARP1-mediated regulation of Pol γ activity.
- To determine how cellular metabolic state influences mtDNA repair efficiency.
Main Methods:
- Biochemical assays to study PARP1 and Pol γ interactions.
- Reconstitution of Pol γ PARylation in vitro.
- Manipulation of NAD+ levels to assess effects on Pol γ activity.
Main Results:
- PARP1 was shown to regulate Pol γ activity in a manner dependent on the metabolic cofactor NAD+.
- In the absence of NAD+, PARP1 completely inhibited Pol γ activity.
- Physiological concentrations of NAD+ restored Pol γ to its maximum DNA repair activity.
Conclusions:
- Mitochondrial DNA repair is directly regulated by PARP1 in a NAD+-dependent manner.
- The efficiency of mtDNA repair is coupled to the cell's metabolic status and the integrity of the respiratory chain.
- This study reveals a direct link between cellular metabolism and the maintenance of mitochondrial genome stability.
Related Concept Videos
02:31Homologous Recombination
02:10Translesion DNA Polymerases
TLS polymerases are found in all three domains of life - archaea, bacteria, and eukaryotes. Of the different classes of TLS polymerases, members of the Y family are fitted with specialized structures that...
02:37DNA Damage can Stall the Cell Cycle
01:38Nucleotide Excision Repair
Cells are regularly exposed to mutagens—factors in the environment that can damage DNA and generate mutations. UV radiation is one of the most common mutagens and is estimated to introduce a significant number of changes in DNA. These include bends or kinks in the structure, which can block DNA replication or transcription. If these errors are not fixed, the damage can cause mutations, which in turn can result in cancer or disease depending on which sequences are...
01:08Nucleotide Excision Repair
02:25Overview of DNA Repair
Chemically...