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Chk2 activates E2F-1 in response to DNA damage
Craig Stevens1, Linda Smith, Nicholas B La Thangue
1Division of Biochemistry and Molecular Biology, Davidson Building, University of Glasgow, Glasgow, G12 8QQ, UK.
Abstract:
The E2F-1 transcription factor is regulated during cell cycle progression and induced by cellular stress, such as DNA damage. We report that checkpoint kinase 2 (Chk2) regulates E2F-1 activity in response to the DNA-damaging agent etoposide. A Chk2 consensus phosphorylation site in E2F-1 is phosphorylated in response to DNA damage, resulting in protein stabilization, increased half-life, transcriptional activation and localization of phosphorylated E2F-1 to discrete nuclear structures. Expression of a dominant-negative Chk2 mutant blocks induction of E2F-1 and prevents E2F-1-dependent apoptosis. Moreover, E2F-1 is resistant to induction by etoposide in tumour cells expressing mutant chk2. Therefore, Chk2 phosphorylates and activates E2F-1 in response to DNA damage, resulting in apoptosis. These results suggest a role for E2F-1 in checkpoint control and provide a plausible explanation for the tumour suppressor activity of E2F-1.
Insights
Checkpoint kinase 2 (Chk2) activates the E2F-1 transcription factor following DNA damage. This Chk2-mediated phosphorylation stabilizes E2F-1, promoting apoptosis and suggesting a role in tumor suppression.
Area of Science:
- Molecular Biology
- Cellular Biology
- Cancer Research
Background:
- E2F-1 transcription factor activity is crucial for cell cycle progression.
- Cellular stress, particularly DNA damage, induces E2F-1.
- Checkpoint kinase 2 (Chk2) is a key regulator in DNA damage response pathways.
Purpose of the Study:
- To investigate the regulatory role of Chk2 in E2F-1 activity upon DNA damage.
- To elucidate the mechanism by which Chk2 influences E2F-1 function and downstream effects.
Main Methods:
- Utilized etoposide as a DNA-damaging agent.
- Analyzed Chk2 phosphorylation of E2F-1 using molecular biology techniques.
- Assessed E2F-1 stabilization, transcriptional activity, and localization.
- Employed dominant-negative Chk2 mutants in cellular assays.
- Examined etoposide-induced apoptosis in tumor cells with wild-type and mutant Chk2.
Main Results:
- Chk2 phosphorylates a specific site on E2F-1 in response to DNA damage.
- Phosphorylation by Chk2 leads to E2F-1 protein stabilization and increased half-life.
- Phosphorylated E2F-1 exhibits enhanced transcriptional activation and distinct nuclear localization.
- Inhibition of Chk2 activity blocks E2F-1 induction and subsequent apoptosis.
- Tumor cells with mutant Chk2 show resistance to etoposide-induced E2F-1 activation.
Conclusions:
- Chk2 directly phosphorylates and activates E2F-1 in response to DNA damage.
- This Chk2-E2F-1 pathway is critical for inducing apoptosis after DNA damage.
- E2F-1 plays a role in DNA damage checkpoint control.
- The findings provide a mechanistic link between Chk2, E2F-1, and tumor suppression.