title: Time and dose-dependent activation of p53 serine 15 phosphorylation among cell lines with different radiation sensitivity.
abstract: OBJECTIVE
  Proper detection of DNA damage and signal transduction to other proteins following irradiation (IR) is essential for cellular integrity. The serine 15 (Ser15) on p53 is crucial for p53 stabilization and a requirement for transient and permanent cell cycle arrest. Here, we sought to determine the relationship between p53 serine 15 phosphorylation (p53-p-Ser15) on cellular sensitivity and if this modification is associated with DNA double-strand break (DSB) repair.
  
  
  METHODS
  Eight lymphoblastoid cell lines including ataxia-telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and radiosensitive patient derived cell lines were irradiated with 1 Gy, 2 Gy and 5 Gy. Then growth inhibition, p53 induction and phosphorylation on Ser15 as assessed by immunoblotting and DNA DSB repair as assessed by constant field gel electrophoresis were examined.
  
  
  RESULTS
  Phosphorylation of p53 at Ser15 in control cells rapidly increased, peaking at 3-6 hours and then sustained a low level of phosphorylation for up to 6 days following IR. For these cell lines, the amount of p53-p-Ser15 corresponded to the sensitivity of cells and the amount of DNA DSB. In A-T cells, p53-p-Ser15 was reduced in spite of increased DNA DSB. NBS cells had similar phosphorylation dynamics as the control cell line, which was not consistent with their increased sensitivity. Radiosensitive patients' cell lines differed only slightly from controls.
  
  
  CONCLUSIONS
  Cells that are competent in signal transduction have p53-p-Ser15 kinetics corresponding to cellular radiosensitivity as assessed by clonogenicity and DNA DSB repair, and cells impaired in signal transduction lack this correspondence. Therefore, using p53-p-Ser15 as a general marker of radiation sensitivity has confounding factors which may impair proper radiosensitivity prediction.
authors.affiliation: Department of Radiation Oncology, Friedrich-Alexander-University Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Wittlinger
authors.forename: Gerhard G
authors.initials: GG
authors.lastname: Grabenbauer
authors.forename: Carl N
authors.initials: CN
authors.lastname: Sprung
authors.forename: Rolf
authors.initials: R
authors.lastname: Sauer
authors.forename: Luitpold V R
authors.initials: LV
authors.lastname: Distel
mesh_terms: D002460:Cell Line; D004247:DNA / Q000235:genetics* / Q000528:radiation effects*; D004249:DNA Damage; D004260:DNA Repair / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D008214:Lymphocytes / Q000502:physiology* / Q000528:radiation effects*; D010766:Phosphorylation / Q000528:radiation effects; D011829:Radiation Dosage; D011836:Radiation Tolerance / Q000502:physiology* / Q000528:radiation effects; D013997:Time Factors; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D004247:DNA