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DNA-dependent protein kinase acts upstream of p53 in response to DNA damage
R A Woo1, K G McLure, S P Lees-Miller
1Department of Microbiology and Infectious Diseases, University of Calgary, Alberta, Canada.
Abstract:
The tumour suppressor p53 becomes activated as a transcription factor in response to DNA damage, but the mechanism for this activation is unclear. A good candidate for an upstream activator of p53 is the DNA-dependent protein kinase (DNA-PK) that depends on the presence of DNA breaks for its activity. Here we investigate the link between DNA damage and the activation of DNA-PK and of p53. To determine whether DNA-PK is an upstream mediator of the p53 DNA-damage response, we analysed a severe combined-immunodeficiency (SCID) mouse cell line, SCGR11, and the human glioma cell line M059J . Both cell lines lack any detectable DNA-PK activity. We find that p53 is incapable of binding to DNA in the absence of DNA-PK, that DNA-PK is necessary but not sufficient for activation of p53 sequence-specific DNA binding, and that this activation occurs in response to DNA damage. Our results establish DNA-PK as a link between DNA damage and p53 activation, and reveal the existence of a mammalian DNA-damage-response pathway.
Insights
DNA-dependent protein kinase (DNA-PK) is essential for activating the tumor suppressor p53 after DNA damage. This study reveals DNA-PK as a key link in the mammalian DNA damage response pathway.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- The tumor suppressor p53 is activated by DNA damage, functioning as a transcription factor.
- The precise mechanism linking DNA damage to p53 activation remains unclear.
- DNA-dependent protein kinase (DNA-PK) is a potential upstream activator, requiring DNA breaks for its function.
Purpose of the Study:
- To investigate the role of DNA-PK in the DNA damage response pathway.
- To determine if DNA-PK acts as an upstream mediator of p53 activation following DNA damage.
- To elucidate the relationship between DNA damage, DNA-PK activity, and p53 activation.
Main Methods:
- Analysis of a severe combined-immunodeficiency (SCID) mouse cell line (SCGR11) lacking DNA-PK activity.
- Analysis of a human glioma cell line (M059J) also lacking DNA-PK activity.
- Assessment of p53 DNA binding and activation in the presence and absence of DNA-PK.
Main Results:
- p53 could not bind to DNA without detectable DNA-PK activity.
- DNA-PK was found to be necessary, but not sufficient, for the sequence-specific DNA binding and activation of p53.
- p53 activation occurred in response to DNA damage, contingent on DNA-PK presence.
Conclusions:
- DNA-dependent protein kinase (DNA-PK) serves as a crucial link between DNA damage and the activation of p53.
- A novel mammalian DNA-damage-response pathway involving DNA-PK and p53 has been identified.
- These findings highlight the critical role of DNA-PK in cellular responses to genomic instability.