Interactions of the DNA ligase IV-XRCC4 complex with DNA ends and the DNA-dependent protein kinase

Ling Chen, Kelly Trujillo, Patrick Sung, Alan E. Tomkinson

Research output: Contribution to journalArticlepeer-review

197 Scopus citations


The DNA-dependent protein kinase (DNA-PK), consisting of Ku and the DNA-PK catalytic subunit (DNA-PKcs), and the DNA ligase IV-XRCC4 complex function together in the repair of DNA double-strand breaks by non-homologous end joining. These protein complexes are also required for the completion of V(D)J recombination events in immune cells. Here we demonstrate that the DNA ligase IV-XRCC4 complex binds specifically to the ends of duplex DNA molecules and can act as a bridging factor, linking together duplex DNA molecules with complementary but non-ligatable ends. Although the DNA end-binding protein Ku inhibited DNA joining by DNA ligase IV-XRCC4, it did not prevent this complex from binding to DNA. Instead, DNA ligase IV-XRCC4 and Ku bound simultaneously to the ends of duplex DNA molecules. DNA ligase IV-XRCC4 and DNA-PKcs also formed complexes at the ends of DNA molecules, but DNA-PKcs did not inhibit ligation. Interestingly, DNA-PKcs stimulated intermolecular ligation by DNA ligase IV-XRCC4. In the presence of DNA-PK, the majority of the joining events catalyzed by DNA ligase IV-XRCC4 were intermolecular because Ku inhibited intramolecular ligation, but DNA-PKcs still stimulated intramolecular ligation. We suggest that DNA-PKcs-containing complexes formed at DNA ends enhance the association of DNA ends via protein-protein interactions, thereby stimulating intermolecular ligation.

Original languageEnglish (US)
Pages (from-to)26196-26205
Number of pages10
JournalJournal of Biological Chemistry
Issue number34
StatePublished - Aug 25 2000
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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