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Sustained CHK2 activity, but not ATM activity, is critical to maintain a G1 arrest after DNA damage in untransformed
Iraia García-Santisteban1,2, Alba Llopis2, Lenno Krenning2
1Department of Genetics, Physical Anthropology and Animal Physiology, University of the Basque Country (UPV/EHU), B/Sarriena s/n, 48940, Leioa, Basque Country, Spain.
Background:
The G1 checkpoint is a critical regulator of genomic stability in untransformed cells, preventing cell cycle progression after DNA damage. DNA double-strand breaks (DSBs) recruit and activate ATM, a kinase which in turn activates the CHK2 kinase to establish G1 arrest. While the onset of G1 arrest is well understood, the specific role that ATM and CHK2 play in regulating G1 checkpoint maintenance remains poorly characterized.
Results:
Here we examine the impact of ATM and CHK2 activities on G1 checkpoint maintenance in untransformed cells after DNA damage caused by DSBs. We show that ATM becomes dispensable for G1 checkpoint maintenance as early as 1 h after DSB induction. In contrast, CHK2 kinase activity is necessary to maintain the G1 arrest, independently of ATM, ATR, and DNA-PKcs, implying that the G1 arrest is maintained in a lesion-independent manner. Sustained CHK2 activity is achieved through auto-activation and its acute inhibition enables cells to abrogate the G1-checkpoint and enter into S-phase. Accordingly, we show that CHK2 activity is lost in cells that recover from the G1 arrest, pointing to the involvement of a phosphatase with fast turnover.
Conclusion:
Our data indicate that G1 checkpoint maintenance relies on CHK2 and that its negative regulation is crucial for G1 checkpoint recovery after DSB induction.
Insights
The G1 checkpoint maintains genomic stability after DNA damage. CHK2 kinase activity, not ATM, is crucial for sustaining this G1 arrest, with its loss enabling cell cycle recovery.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- The G1 checkpoint prevents cell cycle progression post-DNA damage, crucial for genomic stability.
- DNA double-strand breaks (DSBs) activate ATM and CHK2 kinases to initiate G1 arrest.
- The roles of ATM and CHK2 in maintaining G1 arrest are not fully understood.
Purpose of the Study:
- To investigate the roles of ATM and CHK2 in G1 checkpoint maintenance after DSBs.
- To elucidate the mechanisms underlying G1 arrest maintenance and recovery.
Main Methods:
- Analysis of ATM and CHK2 activity in untransformed cells post-DSB induction.
- Assessment of G1 checkpoint status and cell cycle progression.
- Investigation of kinase independence and auto-activation mechanisms.
Main Results:
- ATM is dispensable for G1 checkpoint maintenance 1 hour after DSB induction.
- CHK2 kinase activity is essential for maintaining G1 arrest independently of other kinases.
- Sustained CHK2 auto-activation maintains G1 arrest; its inhibition or loss leads to G1 checkpoint abrogation and S-phase entry.
Conclusions:
- G1 checkpoint maintenance relies on CHK2 activity.
- Negative regulation of CHK2 is critical for G1 checkpoint recovery following DNA damage.
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