title: DNA-PK phosphorylation sites on Oct-1 promote cell survival following DNA damage.
abstract: Octamer transcription factor-1 (Oct-1) has recently been shown to function as a stress sensor that promotes cell survival subsequent to DNA damage. Here, we show that the survival signal imparted by Oct-1 following exposure to ionizing radiation (IR) is dependent upon DNA-dependent protein kinase (DNA-PK)-dependent phosphorylation of a cluster of 13 specific ser/thr residues within the N-terminal transcriptional regulatory domain of Oct-1. Although IR treatment did not affect the recruitment of Oct-1 to the histone H2B promoter, the recruitment of RNA polymerase II, TATA-binding protein and histone H4 acetylation were strongly reduced, consistent with a decrease in Oct-1 transcriptional regulatory potential following IR exposure. Ser/Thr-Ala substitution of 13 sites present in Oct-1 transcriptional regulatory domain eliminated Oct-1 phosphorylation subsequent to IR exposure. Further, these substitutions prevented Oct-1 from rescuing the survival of IR-treated Oct-1-/- murine embryonic fibroblasts, providing a direct link between DNA-PK-dependent phosphorylation and the contribution of Oct-1 to cell survival. These results implicate Oct-1 as a primary effector in a DNA-PK-dependent cell survival pathway that is activated by double-stranded DNA breaks.
authors.affiliation: Department of Medicine, The Ottawa Health Research Institute, University of Ottawa, Ottawa, Ontario, Canada. cschild-poulter@robarts.ca
authors.forename: C
authors.initials: C
authors.lastname: Schild-Poulter
authors.forename: A
authors.initials: A
authors.lastname: Shih
authors.forename: D
authors.initials: D
authors.lastname: Tantin
authors.forename: N C
authors.initials: NC
authors.lastname: Yarymowich
authors.forename: S
authors.initials: S
authors.lastname: Soubeyrand
authors.forename: P A
authors.initials: PA
authors.lastname: Sharp
authors.forename: R J G
authors.initials: RJ
authors.lastname: Haché
mesh_terms: D016475:3T3 Cells; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D001665:Binding Sites; D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000235:genetics / Q000528:radiation effects; D004249:DNA Damage; D051747:DNA-Activated Protein Kinase / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D006657:Histones / Q000235:genetics; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D050811:Octamer Transcription Factor-1 / Q000235:genetics* / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000528:radiation effects; D012694:Serine / Q000235:genetics / Q000378:metabolism; D013912:Threonine / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: D006657:Histones; D050811:Octamer Transcription Factor-1; D013912:Threonine; D012694:Serine; D051747:DNA-Activated Protein Kinase