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Yeast As a Chassis for Developing Functional Assays to Study Human P53
Published on: August 4, 2019
The Chk2 tumor suppressor is not required for p53 responses in human cancer cells
Prasad V Jallepalli1, Christoph Lengauer, Bert Vogelstein
1The Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Johns Hopkins University, Baltimore, Maryland 21231, USA. bunzfre@mail.jhmi.edu
Abstract:
Ionizing radiation damages chromosomal DNA and activates p53-dependent transcription in mammalian cells. The Chk2 protein kinase has been hypothesized to be the primary mediator of this response. We have rigorously tested this hypothesis in human cells by disrupting the CHK2 gene through homologous recombination. We found that the p53 response was unexpectedly robust in such cells. Phosphorylation of p53 at serine 20, accumulation of p53 protein, transcriptional activation of p53 target genes, and cell cycle arrest and apoptotic death phenotypes were completely intact regardless of CHK2 status. Our results indicate that Chk2 kinase is not required for p53 activation in human cells and explain why CHK2 and TP53 mutations can jointly occur in human tumors.
Insights
Chk2 protein kinase is not essential for the p53 response in human cells following DNA damage. The p53 pathway remains robust, even without functional Chk2, explaining co-occurring mutations in tumors.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Ionizing radiation induces DNA damage, triggering p53-dependent transcription in mammalian cells.
- The Chk2 protein kinase has been proposed as a key mediator of this radiation-induced p53 response.
Purpose of the Study:
- To rigorously test the hypothesis that Chk2 is the primary mediator of the p53 response to ionizing radiation in human cells.
Main Methods:
- Disruption of the CHK2 gene in human cells using homologous recombination.
- Assessment of p53 phosphorylation, protein accumulation, target gene transactivation, cell cycle arrest, and apoptosis.
Main Results:
- The p53 response, including phosphorylation at serine 20, protein accumulation, transcriptional activation, cell cycle arrest, and apoptosis, was completely intact in CHK2-disrupted cells.
- These phenotypes were unaffected by the absence of functional Chk2 kinase.
Conclusions:
- Chk2 kinase is not required for the activation of the p53 pathway in human cells following DNA damage.
- This finding helps explain the frequent co-occurrence of CHK2 and TP53 mutations in human tumors.
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