title: ATR-dependent phosphorylation of DNA-dependent protein kinase catalytic subunit in response to UV-induced replication stress.
abstract: Phosphorylation of the DNA-dependent protein kinase catalytic subunit (DNA-PKcs) upon ionizing radiation (IR) is essential for cellular radioresistance and nonhomologous-end-joining-mediated DNA double-strand break repair. In addition to IR induction, we have previously shown that DNA-PKcs phosphorylation is increased upon camptothecin treatment, which induces replication stress and replication-associated double-strand breaks. To clarify the involvement of DNA-PKcs in this process, we analyzed DNA-PKcs phosphorylation in response to UV irradiation, which causes replication stress and activates ATR (ATM-Rad3-related)/ATM (ataxia-telangiectasia mutated) kinases in a replication-dependent manner. Upon UV irradiation, we observed a rapid DNA-PKcs phosphorylation at T2609 and T2647, but not at S2056, distinct from that induced by IR. UV-induced DNA-PKcs phosphorylation occurs specifically only in replicating cells and is dependent on ATR kinase. Inhibition of ATR activity via caffeine, a dominant-negative kinase-dead mutant, or RNA interference led to the attenuation of UV-induced DNA-PKcs phosphorylation. Furthermore, DNA-PKcs associates with ATR in vivo and is phosphorylated by ATR in vitro, suggesting that DNA-PKcs could be the direct downstream target of ATR. Taken together, these results strongly suggest that DNA-PKcs is required for the cellular response to replication stress and might play an important role in the repair of stalled replication forks.
authors.affiliation: Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, 2201 Inwood Rd., NC7.502, Dallas, TX 75390-9187, USA.
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Yajima
authors.forename: Kyung-Jong
authors.initials: KJ
authors.lastname: Lee
authors.forename: Benjamin P C
authors.initials: BP
authors.lastname: Chen
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D020134:Catalytic Domain; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D004247:DNA / Q000235:genetics*; D004249:DNA Damage / Q000528:radiation effects; D004260:DNA Repair; D004261:DNA Replication / Q000528:radiation effects*; D051747:DNA-Activated Protein Kinase / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation / Q000528:radiation effects; D010769:Phosphothreonine / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016196:S Phase / Q000235:genetics / Q000528:radiation effects; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D025521:Tumor Suppressor Proteins; D010769:Phosphothreonine; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases