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ATR pathway is the primary pathway for activating G2/M checkpoint induction after re-replication
Jie Jessie Lin1, Anindya Dutta
1Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia 22908, USA.
The Journal of Biological Chemistry
|August 25, 2007
Summary
Geminin inactivation causes DNA re-replication in tumor cells, activating the ATR/Chk1 pathway for early cell cycle arrest. The ATM/Chk2 pathway is activated later as a consequence of this re-replication.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- DNA replication requires precise control to ensure genomic stability.
- Geminin is a key inhibitor of DNA replication origin licensing.
- Loss of Geminin can lead to uncontrolled DNA re-replication and genomic instability in cancer cells.
Purpose of the Study:
- To investigate the signaling pathways involved in detecting and responding to DNA re-replication.
- To elucidate the roles of ATR and ATM kinases in the checkpoint response to Geminin inactivation.
Main Methods:
- Human tumor cells with Geminin inactivation were analyzed.
- Activation of checkpoint kinases (ATR, ATM, Chk1, Chk2) and associated protein complexes (9-1-1 clamp, Mre11-Rad50-Nbs1) were assessed.
Main Results:
- ATR kinase and the 9-1-1 clamp complex, with Rad17-RFC, are the primary sensors of DNA re-replication upon Geminin loss.
- Chk1 activation is early, while Chk2 activation is delayed, suggesting distinct pathway kinetics.
- ATM kinase and the Mre11-Rad50-Nbs1 complex play minor roles in this specific checkpoint response.
Conclusions:
- The ATR/Chk1 pathway is crucial for early checkpoint arrest following Geminin inactivation, preventing further cell cycle progression.
- ATM/Chk2 pathway activation is a later event, likely a consequence of ongoing DNA re-replication, rather than an initial trigger.
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