Table 1.
Major eukaryotic NHEJ proteins
| Category | Protein | c-NHEJ | alt-NHEJ | Description |
|---|---|---|---|---|
| DNA-PK | Ku70 | + | − | DSB recognition, dRP lyase |
| Ku80 | + | − | Ku70 partner protein | |
| DNA-PKcs | + | − | DSB-dependent protein kinase | |
| Ligase | Lig4 | + | − | Ligase catalytic subunit |
| XRCC4 | + | − | Lig4 structural scaffold | |
| XLF | + | − | Lig4 structural scaffold | |
| Lig1 | − | +/− | Ligase catalytic subunit | |
| Lig3 | − | + | Ligase catalytic subunit | |
| XRCC1 | − | +/− | Lig3 structural scaffold | |
| MRN | Mre11 | + | + | Dimerization, nuclease |
| Rad50 | + | + | Regulatory ATPase | |
| Nbs1 | + | + | Protein recruitment | |
| PARP | PARP-1 | +/− | + | Poly-ADP ribose polymerase |
| PARP-3 | + | Poly-ADP ribose polymerase | ||
| Polymerase | Pol μ | + | Gap filling | |
| Pol λ | + | Gap filling, dRP lyase | ||
| Nuclease | Artemis | + | Endo/5′ exonuclease | |
| Tdp1 | + | 3′ phosphoesterase | ||
| APLF | + | Endo/3′ exonuclease | ||
| CtIP | + | Supports 5′ resection | ||
| Other | PNKP | + | 5′ kinase, 3′ phosphatase | |
| Aprataxin | + | 5′-AMP intermediate removal |
A summary of NHEJ proteins discussed in the text, with a focus on structural and enzymatic components. This list is not exhaustive because other proteins have been suggested to influence NHEJ. (+) Described role in c-NHEJ or alt-NHEJ; (−) not involved by definitions of c-NHEJ and alt-NHEJ; (+/−) conflicting reports or uncertain role.