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ATM mediates phosphorylation at multiple p53 sites, including Ser(46), in response to ionizing radiation
Shin'ichi Saito1, Aaron A Goodarzi, Yuichiro Higashimoto
1Biology Department, Brookhaven National Laboratory, 50 Bell Avenue, Upton, New York 11973, USA.
Abstract:
The p53 tumor suppressor protein preserves genome integrity by regulating growth arrest and apoptosis in response to DNA damage. In response to ionizing radiation (IR), ATM, the gene product mutated in ataxia telangiectasia, stabilizes and activates p53 through phosphorylation of Ser(15) and (indirectly) Ser(20). Here we show that phosphorylation of p53 on Ser(46), a residue important for p53 apoptotic activity, as well as on Ser(9), in response to IR also is dependent on the ATM protein kinase. IR-induced phosphorylation at Ser(46) was inhibited by wortmannin, a phosphatidylinositol 3-kinase inhibitor, but not PD169316, a p38 MAPK inhibitor. p53 C-terminal acetylation at Lys(320) and Lys(382), which may stabilize p53 and activate sequence-specific DNA binding, required Ser(15) phosphorylation by ATM and was enhanced by phosphorylation at nearby residues including Ser(6), Ser(9), and Thr(18). These observations, together with the proposed role of Ser(46) phosphorylation in mediating apoptosis, suggest that ATM is involved in the initiation of p53-dependent apoptosis after IR in human lymphoblastoid cells.
Insights
The ATM protein kinase is crucial for initiating p53-dependent apoptosis after ionizing radiation (IR) by phosphorylating p53 at key sites. This ATM-mediated phosphorylation regulates p53
Area of Science:
- Molecular Biology
- Cancer Research
- Cellular Signaling
Background:
- The p53 tumor suppressor protein is vital for maintaining genome stability through regulated growth arrest and apoptosis following DNA damage.
- ATM (ataxia telangiectasia mutated) kinase is known to stabilize and activate p53 after ionizing radiation (IR) via phosphorylation at Ser(15) and Ser(20).
Purpose of the Study:
- To investigate the role of ATM protein kinase in the phosphorylation of p53 at Ser(46) and Ser(9) in response to IR.
- To elucidate the relationship between ATM-dependent p53 phosphorylation and subsequent C-terminal acetylation.
- To determine ATM's involvement in initiating p53-dependent apoptosis after IR.
Main Methods:
- Investigated IR-induced phosphorylation of p53 on Ser(46) and Ser(9) in human lymphoblastoid cells.
- Utilized wortmannin (a PI3K inhibitor) and PD169316 (a p38 MAPK inhibitor) to assess signaling pathways.
- Examined ATM-dependent p53 C-terminal acetylation at Lys(320) and Lys(382) in relation to phosphorylation events.
Main Results:
- IR-induced phosphorylation of p53 at Ser(46) and Ser(9) was dependent on ATM kinase activity.
- Phosphorylation at Ser(46) was sensitive to wortmannin but not PD169316, suggesting PI3K pathway involvement.
- p53 acetylation at Lys(320) and Lys(382) required ATM-mediated Ser(15) phosphorylation and was enhanced by other phosphorylation sites.
Conclusions:
- ATM kinase plays a critical role in regulating p53 phosphorylation at Ser(46) and Ser(9) following IR.
- ATM-dependent phosphorylation events are essential for subsequent p53 acetylation and sequence-specific DNA binding.
- These findings strongly suggest ATM's involvement in initiating p53-dependent apoptosis after IR exposure.