Table 1.
| DNA-PKcs | ATM | ATR | |
|---|---|---|---|
| DNA tethering complex |
Ku70/80 |
MRN |
RPA, Rad9/Rad1/Hus1 |
| H2AX/MDC1 | |||
| Activating protein |
Ku80 |
Nbs1 |
ATRIP |
| Activating DNA substrates |
ds-DNA termini, higher activation with 5′ ss overhangs |
Long 3′ ss regions |
Short 3′ ss regions near ds junctions |
| Unique phosphorylation targets |
Multiple sites of autophosphorylation |
Chk2 |
Chk1 |
| RPA phosphorylation |
Ser 4, Ser 8, Ser 12 |
Ser 33 |
|
| Ser 21 | |||
| Quaternary structure | Dimer when active | Dimer when inactive | Multimer upon activation in complex wih RPA |