[Interaction between ATM and radiation-activated phosphorylation of P53 and P21].

Background & Objective: ATM gene is a member of PI-3K kinase family. ATM protein is capable of controlling DNA repair process and cell cycle checkpoint. In AT cells from ataxia-telangiectasia (AT) patients, ATM gene mutation leads to the deficiency of ionizing radiation-activated phosphorylation of P53 and P21. It shows ATM gene could mediate the phosphorylation of P53 and P21. This study was to explore the interaction between ATM and P53, and to observe whether ATM directly medicates the phosphorylation of P21 in a P53-independent way.
Methods: pEBS7-YZ5 vector containing ATM cDNA was transfected into AT cells by electroperforation. The cells expressing ATM protein stably were screened with hygromycin, and identified by reverse transcription-polymerase chain reaction (RT-PCR). The interaction between ATM and P53 in pEBS7-YZ5-AT cells was assessed by co-immunoprecipitation and Western blot. K562 cells served as a P53 mutation cell model to study whether ATM could interact with the phosphorylation of P21.
Results: pEBS7-YZ5 was transfected into AT cells successfully. RT-PCR detected fragment of ATM cDNA. After exposed to ionizing radiation, P53 of pEBS7-YZ5-AT cells was phosphorylated, and immunoprecipitation showed interaction between ATM and P53; P21 of K562 cells was phosphorylated, P21 protein was detected in the immunoprecipitation of ATM antibody-complex.
Conclusion: Ionizing radiation-activated ATM kinase could interact with the phosphorylation of P53 and P21 in both P53 wild type and mutant type cells.