The POLM gene encodes DNA polymerase mu (Pol μ), a member of the X-family DNA polymerases. Pol μ is primarily involved in non-homologous end joining (NHEJ) repair of DNA double-strand breaks and plays a critical role in V(D)J recombination. Unlike other DNA polymerases, Pol μ can catalyze template-independent nucleotide incorporation, making it uniquely suited for repairing DNA ends with incompatible overhangs.
| Attribute | Value |
|---|---|
| Symbol | POLM |
| Full Name | DNA Polymerase Mu |
| Chromosomal Location | 7p13 |
| NCBI Gene ID | 11298 |
| OMIM | 605515 |
| Ensembl ID | ENSG00000157212 |
| UniProt | Q9NP87 |
DNA polymerase mu (Pol μ) is a specialized DNA polymerase that performs several critical functions in DNA repair and immune system development:
Pol μ plays a specialized role in the NHEJ pathway for DNA double-strand break repair:
Unlike other polymerases, Pol μ can incorporate multiple nucleotides without template guidance, making it uniquely suited for repairing ends with variable overhangs.
During V(D)J recombination, Pol μ contributes to:
DNA polymerase mu (Pol μ, ~494 amino acids, ~55 kDa) is structurally unique among X-family polymerases:
The unique ability of Pol μ to incorporate nucleotides without a template (template-independent synthesis) makes it essential for filling gaps during NHEJ repair of incompatible DNA ends.
In Alzheimer's disease, impaired NHEJ repair contributes to neurodegeneration:
DNA Double-Strand Break Accumulation: Neurons in AD brain show elevated levels of DNA double-strand breaks. Reduced NHEJ efficiency, potentially involving Pol μ dysfunction, may contribute to this accumulation.
Activity-Dependent DNA Repair: Neurons require DNA repair during synaptic activity. Pol μ-mediated NHEJ is critical for maintaining genomic integrity in active neurons.
Therapeutic Implications: Enhancing NHEJ through Pol μ upregulation may:
In Parkinson's disease, defective DNA repair contributes to dopaminergic neuron loss:
Pol μ and ATM deficiency have synergistic effects:
| Disease | Mechanism | Evidence |
|---|---|---|
| Alzheimer's Disease | Impaired NHEJ repair leads to accumulation of DNA double-strand breaks in neurons | Reduced NHEJ efficiency observed in AD brain tissue [1] |
| Parkinson's Disease | Defective DNA repair contributes to dopaminergic neuron loss | DNA repair deficits documented in PD models |
| Ataxia-Telangiectasia | NHEJ defects compound ATM deficiency | Synergistic effects with ATM deficiency |
POLM mutations cause immunodeficiency syndrome with defective V(D)J recombination, leading to:
Pol μ dysregulation is associated with:
Mice lacking Pol μ exhibit:
Pol μ/Pol λ double deficiency leads to:
Pol μ inhibitors and modulators may be useful in:
Potential therapeutic strategies include: