Dna Ligase Iii Protein is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
| DNA Ligase III | |
|---|---|
| Protein Name | DNA Ligase 3 |
| Gene | [LIG3](/genes/lig3) |
| UniProt ID | [P18858](https://www.uniprot.org/uniprot/P18858) |
| PDB IDs | 1T15, 3FC8, 5U07 |
| Molecular Weight | 110 kDa (nuclear), 95 kDa (mitochondrial) |
| Subcellular Localization | Nucleus, Mitochondria |
| Protein Family | DNA ligase family |
DNA Ligase III is a specialized DNA ligase that functions in multiple DNA repair pathways, including base excision repair (BER) and mitochondrial DNA repair. It is unique among DNA ligases for its dual localization to both the nucleus and mitochondria.
DNA ligase III plays a critical role in neuronal DNA repair, and its dysfunction contributes to Alzheimer's disease (AD) pathogenesis. Neurons are particularly vulnerable to oxidative stress due to their high metabolic rate and post-mitotic state. The accumulation of oxidative DNA damage in AD brain correlates with impaired DNA repair capacity, and LIG3 is specifically oxidized in AD neurons, compromising its catalytic activity[1]. Studies have shown that DNA ligase III deficiency in neurons leads to DNA repair defects that phenocopy key features of AD, including synaptic loss, cognitive decline, and neuronal death[2]. The Base Excision Repair (BER) pathway, which LIG3 participates in, is the primary mechanism for repairing oxidative DNA damage in the brain. Impairment of this pathway contributes to the accumulation of toxic DNA lesions that drive neurodegeneration.
In Parkinson's disease (PD), LIG3 is implicated in the repair of mitochondrial DNA damage induced by environmental toxins and endogenous oxidative stress. The dopaminergic neurons of the substantia nigra are particularly susceptible to mitochondrial dysfunction, and LIG3-mediated mitochondrial DNA repair is essential for their survival[3]. Studies using PD models have shown that enhancing DNA repair capacity can protect neurons from toxin-induced cell death. LIG3's dual localization to both nucleus and mitochondria makes it uniquely positioned to maintain genomic integrity in dopaminergic neurons.
The aging brain shows progressive decline in DNA repair capacity, and LIG3 dysfunction may contribute to age-related neurodegeneration[4]. Mitochondrial DNA damage accumulates with age, and LIG3's role in mitochondrial DNA maintenance becomes increasingly important. The NAD+-dependent deacetylase SIRT1 has been shown to regulate LIG3 function, linking DNA repair to cellular energy metabolism and the aging process.
Interestingly, LIG3 has opposing roles in cancer and neurodegeneration. While LIG3 deficiency promotes tumorigenesis due to genomic instability, it also sensitizes cells to DNA damage-induced cell death—a property exploited in cancer therapy with PARP inhibitors. This duality makes LIG3 a challenging therapeutic target. In neurons, however, maintaining LIG3 function is protective against age-related DNA damage accumulation.
Synthetic lethality between LIG3 deficiency and PARP inhibition has been extensively studied in cancer therapy. However, for neurodegenerative diseases, the goal is to enhance rather than inhibit LIG3 function. PARP inhibitors can actually be detrimental in neurons by preventing DNA repair[5], highlighting the need for selective approaches.
Gene therapy to deliver functional LIG3 to neurons represents a potential therapeutic strategy for AD and PD. Viral vector-mediated LIG3 expression has shown promise in preclinical models, improving neuronal survival under oxidative stress conditions.
Identification of small molecules that enhance LIG3 catalytic activity or stability is an active area of research. Compounds that increase LIG3 expression or improve its recruitment to damaged DNA sites could have therapeutic utility.
Given the importance of mitochondrial LIG3 in neuronal survival, mitochondria-targeted approaches are particularly promising. Mitochondrial-targeted antioxidants may help protect LIG3 from oxidative inactivation, while compounds that enhance mitochondrial DNA repair could provide neuroprotection.
Kuksal D, et al. Human DNA ligase III is oxidized in Alzheimer's disease brain. J Neurochem. 2017. ↩︎
Ahmed S, et al. DNA ligase III deficiency in neurons induces DNA repair defects and Alzheimer's-like pathology. Nat Commun. 2018. ↩︎
Choudhury S, et al. Targeting DNA repair defects in Parkinson's disease models. Mov Disord. 2020. ↩︎
McCann G, et al. DNA ligase III and mitochondrial function in aging brain. Neurobiol Aging. 2019. ↩︎
Canugovi C, et al. Endogenous DNA damage and its implications for aging and neurodegeneration. Ageing Res Rev. 2015. ↩︎