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Rad9 modulates the P21WAF1 pathway by direct association with p53
Kazuhiro Ishikawa1, Hideshi Ishii, Yoshiki Murakumo
1Department of Otolaryngology-Head and Neck Surgery, Jichi Medical University School of Medicine, Tochigi, Japan. kazu-ish@jichi.ac.jp <kazu-ish@jichi.ac.jp>
BMC Molecular Biology
|May 22, 2007
Summary
Human RAD9 (hRad9) directly regulates P21WAF1 transcription through p53-dependent mechanisms. Phosphorylation of hRad9 is crucial for this process, impacting DNA damage checkpoint activation in cancer.
Area of Science:
- Molecular Biology
- Cancer Research
- Cell Cycle Regulation
Background:
- Human RAD9 (hRad9) is amplified in various epithelial tumors.
- hRad9 is implicated in regulating the tumor suppressor p53-dependent transactivation of P21WAF1.
- The precise mechanism of hRad9's role, particularly C-terminal phosphorylation, in P21WAF1 transcription requires elucidation.
Purpose of the Study:
- To investigate the exact mechanism of hRad9 function in P21WAF1 transcription regulation.
- To determine the role of hRad9 C-terminal phosphorylation in this process.
Main Methods:
- Transfection of phosphorylation-defective hRAD9 mutants.
- Knockdown of total hRad9.
- Immunoprecipitation assays.
- Chromatin immunoprecipitation (ChIP) assays.
Main Results:
- Phosphorylation-defective hRAD9 mutants reduced p53-dependent P21WAF1 transactivation.
- hRad9 knockdown increased P21WAF1 mRNA expression.
- hRad9 and p53 form a complex associated with P21WAF1 gene regulatory regions.
- This association was diminished with phosphorylation-defective hRAD9 mutants.
Conclusions:
- hRad9 directly participates in the p53-dependent P21WAF1 transcriptional mechanism.
- Phosphorylation sites on hRad9 are likely critical for its function.
- Dysregulation of the hRad9 pathway may contribute to impaired checkpoint activation in cancer cells.
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