| First Author | Smits VA | Year | 2006 |
| Journal | Curr Biol | Volume | 16 |
| Issue | 2 | Pages | 150-9 |
| PubMed ID | 16360315 | Mgi Jnum | J:106236 |
| Mgi Id | MGI:3617920 | Doi | 10.1016/j.cub.2005.11.066 |
| Citation | Smits VA, et al. (2006) Rapid PIKK-dependent release of Chk1 from chromatin promotes the DNA-damage checkpoint response. Curr Biol 16(2):150-9 |
| abstractText | BACKGROUND: Checkpoint signaling pathways are of crucial importance for the maintenance of genomic integrity. Within these pathways, the effector kinase Chk1 plays a central role in mediating cell-cycle arrest in response to DNA damage, and it does so by phosphorylating key cell-cycle regulators. RESULTS: By investigating the subcellular distribution of Chk1 by cell fractionation, we observed that around 20% of it localizes to chromatin during all phases of the cell cycle. Furthermore, we found that in response to DNA damage, Chk1 rapidly dissociates from the chromatin. Significantly, we observed a tight correlation between DNA-damage-induced Chk1 phosphorylation and chromatin dissociation, suggesting that phosphorylated Chk1 does not stably associate with chromatin. Consistent with these events being triggered by active checkpoint signaling, inhibition of the DNA-damage-activated kinases ATR and ATM, or siRNA-mediated downregulation of the DNA-damage mediator proteins Claspin and TopBP1, impaired DNA-damage-induced dissociation of Chk1 from chromatin. Finally, we established that Chk1 phosphorylation occurs at localized sites of DNA damage and that constitutive immobilization of Chk1 on chromatin results in a defective DNA-damage-induced checkpoint arrest. CONCLUSIONS: Chromatin association and dissociation appears to be important for proper Chk1 regulation. We propose that in response to DNA damage, PIKK-dependent checkpoint signaling leads to phosphorylation of chromatin-bound Chk1, resulting in its rapid release from chromatin and facilitating the transmission of DNA-damage signals to downstream targets, thereby promoting efficient cell-cycle arrest. |
