DNA Double-Strand Break Formation upon UV-Induced Replication Stress Activates ATM and DNA-PKcs Kinases

Hirohiko Yajima, Kyung Jong Lee, Shichuan Zhang, Junya Kobayashi, Benjamin P C Chen

Research output: Contribution to journalArticlepeer-review

102 Scopus citations


The phosphatidylinositol 3-kinase-like protein kinases, including ATM (ataxia-telangiectasia mutated), ATR (ataxia-telangiectasia and Rad3 related), and DNA-PKcs (DNA-dependent protein kinase catalytic subunit), are the main kinases activated following various assaults on DNA. Although ATM and DNA-PKcs kinases are activated upon DNA double-strand breaks, evidence suggests that these kinases are rapidly phosphorylated by ATR kinase upon UV irradiation; thus, these kinases may also participate in the response to replication stress. Using UV-induced replication stress, we further characterize whether ATM and DNA-PKcs kinase activities are also involved in the cellular response. Contrary to the rapid activation of the ATR-dependent pathway, ATM-dependent Chk2 and KAP-1 phosphorylations, as well as DNA-PKcs Ser2056 autophosphorylation, reach their peak level at 4 to 8 h after UV irradiation. The delayed kinetics of ATM- and DNA-PKcs-dependent phosphorylations also correlated with a surge in H2AX phosphorylation, suggesting that double-strand break formation resulting from collapse of replication forks is responsible for the activation of ATM and DNA-PKcs kinases. In addition, we observed that some phosphorylation events initiated by ATR kinase in the response to UV were mediated by ATM at a later phase of the response. Furthermore, the S-phase checkpoint after UV irradiation was defective in ATM-deficient cells. These results suggest that the late increase of ATM activity is needed to complement the decreasing ATR activity for maintaining a vigilant checkpoint regulation upon replication stress.

Original languageEnglish (US)
Pages (from-to)800-810
Number of pages11
JournalJournal of Molecular Biology
Issue number3
StatePublished - Jan 23 2009


  • ATM
  • DNA double-strand breaks
  • DNA-PKcs
  • UV
  • replication stress

ASJC Scopus subject areas

  • Structural Biology
  • Molecular Biology


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