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| Symbol |
NHEJ1 |
| Full Name |
Non-Homologous End Joining Factor 1 |
| Chromosome |
2q33.3 |
| NCBI Gene |
2004 |
| Ensembl |
ENSG00000168421 |
| OMIM |
607351 |
| UniProt |
Q9GZL0 |
| Diseases |
[Ataxia-Telangiectasia](/diseases/ataxia-telangiectasia), [Parkinson's Disease](/diseases/parkinsons-disease), Immunodeficiency |
| Expression |
Brain (ubiquitous), Thymus, Spleen, Testis |
NHEJ1 (Non-Homologous End Joining Factor 1), also known as XLF or Cernunnos, is a gene located on chromosome 2q33.3 that encodes a core component of the non-homologous end joining (NHEJ) DNA repair pathway. NHEJ is the primary mechanism for repairing DNA double-strand breaks (DSBs) in mammalian cells and is essential for V(D)J recombination in lymphocyte development. Mutations in NHEJ1 cause a severe immunodeficiency syndrome, and defective NHEJ is associated with increased genomic instability and cancer risk. Recent research suggests NHEJ dysfunction may also contribute to neurodegeneration.
The protein encoded by NHEJ1 is available at NHEJ1 Protein.
NHEJ1 forms a complex with XRCC4 and DNA ligase IV to complete the final ligation step in NHEJ repair:
- DNA double-strand break repair: Joins DNA ends that lack homologous sequences
- V(D)J recombination: Essential for antigen receptor gene rearrangement in B and T cells
- Telomere maintenance: Involved in alternative lengthening of telomeres
- Genomic stability: Prevents chromosomal translocations and deletions
NHEJ1 is expressed in multiple brain regions:
Expression is generally ubiquitous, with higher levels in proliferating cells.
NHEJ deficiency leads to progressive DNA damage accumulation in post-mitotic neurons:
- Neurons accumulate DNA double-strand breaks over time
- Impaired repair leads to genomic instability
- DNA damage triggers apoptotic pathways
NHEJ1 interacts with ATM (Ataxia-Telangiectasia Mutated) kinase:
- ATM activates DNA damage checkpoints
- Combined defects cause severe neurodegeneration
- Ataxia-telangiectasia patients show progressive cerebellar degeneration
Recent studies suggest NHEJ dysfunction may contribute to PD:
- Dopaminergic neurons are particularly vulnerable to DNA damage
- Mitochondrial DNA damage may be especially relevant
- PARP1 hyperactivation can deplete NAD+ and energy reserves
¶ Aging and Neurodegeneration
DNA repair capacity declines with age:
- NHEJ efficiency decreases in aging neurons
- Accumulated damage contributes to age-related neurodegeneration
- Therapeutic enhancement of NHEJ may have anti-aging effects
- Caused by NHEJ1 mutations
- Milder than AT due to partial NHEJ function
- Cerebellar ataxia and immunodeficiency
- NHEJ1 variants may modify PD risk
- DNA damage response pathways are impaired in PD brains
- Interaction with PINK1/Parkin mitophagy pathways
- NHEJ1 deficiency increases cancer risk
- Chromosomal translocations are more frequent
- Particularly important in lymphoid malignancies
Targeting NHEJ may offer therapeutic benefits:
- Small molecules to enhance NHEJ efficiency
- Gene therapy to restore NHEJ1 function
- Antioxidants to reduce oxidative DNA damage
Strategies for neuroprotection include:
- PARP inhibitors to prevent excessive energy depletion
- NAD+ supplementation to support DNA repair
- Mitochondrial-targeted antioxidants
- Cernunnos/XLF regulates the kinetics of DNA end joining. Cell, 2006. PMID: 16809985
- Non-homologous end joining and neurodegenerative disease. DNA Repair, 2020. PMID: 32771837
- DNA damage and repair in neurodegeneration. Neurobiology of Aging, 2019. PMID: 30639256