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Enhanced phosphorylation of p53 by ATM in response to DNA damage
1Department of Human Genetics and Molecular Medicine, Sackler School of Medicine, Tel Aviv University, Ramat Aviv 69978, Israel.
Abstract:
The ATM protein, encoded by the gene responsible for the human genetic disorder ataxia telangiectasia (A-T), regulates several cellular responses to DNA breaks. ATM shares a phosphoinositide 3-kinase-related domain with several proteins, some of them protein kinases. A wortmannin-sensitive protein kinase activity was associated with endogenous or recombinant ATM and was abolished by structural ATM mutations. In vitro substrates included the translation repressor PHAS-I and the p53 protein. ATM phosphorylated p53 in vitro on a single residue, serine-15, which is phosphorylated in vivo in response to DNA damage. This activity was markedly enhanced within minutes after treatment of cells with a radiomimetic drug; the total amount of ATM remained unchanged. Various damage-induced responses may be activated by enhancement of the protein kinase activity of ATM.
Insights
The ATM protein kinase activity increases rapidly after DNA damage, phosphorylating p53 at serine-15. This suggests ATM
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Ataxia telangiectasia (A-T) is a human genetic disorder linked to the ATM gene.
- The ATM protein plays a crucial role in cellular responses to DNA breaks.
- ATM contains a phosphoinositide 3-kinase-related domain and exhibits protein kinase activity.
Purpose of the Study:
- To investigate the protein kinase activity of ATM in response to DNA damage.
- To identify in vitro substrates of ATM.
- To explore the mechanism by which ATM regulates DNA damage responses.
Main Methods:
- Assessing wortmannin-sensitive protein kinase activity associated with ATM.
- Using recombinant and endogenous ATM in in vitro kinase assays.
- Treating cells with radiomimetic drugs to induce DNA damage and analyzing ATM activity.
Main Results:
- ATM exhibits wortmannin-sensitive protein kinase activity, abolished by ATM mutations.
- ATM phosphorylates PHAS-I and p53 in vitro.
- ATM phosphorylates p53 at serine-15, a site modified in vivo upon DNA damage.
- This kinase activity is rapidly enhanced after DNA damage, while total ATM levels remain constant.
Conclusions:
- The protein kinase activity of ATM is enhanced rapidly following DNA damage.
- Enhanced ATM kinase activity may activate various damage-induced cellular responses.
- ATM-mediated phosphorylation of p53 at serine-15 is a key event in DNA damage signaling.