title: Defining interactions between DNA-PK and ligase IV/XRCC4.
abstract: Non-homologous end joining (NHEJ) is a major pathway for the repair of DNA double-strand breaks (DSBs) in mammalian cells. DNA-dependent protein kinase (DNA-PK), ligase IV, and XRCC4 are all critical components of the NHEJ repair pathway. DNA-PK is composed of a heterodimeric DNA-binding component, Ku, and a large catalytic subunit, DNA-PKcs. Ligase IV and XRCC4 associate to form a multimeric complex that is also essential for NHEJ. DNA-PK and ligase IV/XRCC4 interact at DNA termini which results in stimulated ligase activity. Here, we define interactions between the components of these two essential complexes, DNA-PK and ligase IV/XRCC4. We find that ligase IV/XRCC4 associates with DNA-PK in a DNA-independent manner. The specific protein-protein interactions that mediate the interaction between these two complexes are further identified. Direct interactions between ligase IV and Ku as well as between XRCC4 and DNA-PKcs are shown. In contrast, binding of ligase IV to DNA-PKcs or XRCC4 to Ku is very weak or non-existent. Our data defines the specific protein pairs involved in the association of DNA-PK and ligase IV/XRCC4, and suggests a molecular mechanism for coordinating the assembly of the DNA repair complex at DNA breaks.
authors.affiliation: Department of Cell and Molecular Biology, Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Hsin Ling
authors.initials: HL
authors.lastname: Hsu
authors.forename: Steven M
authors.initials: SM
authors.lastname: Yannone
authors.forename: David J
authors.initials: DJ
authors.lastname: Chen
mesh_terms: D015153:Blotting, Western; D004247:DNA / Q000378:metabolism; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D066298:In Vitro Techniques; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D014176:Protein Biosynthesis; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D046911:Macromolecular Substances; D009687:Nuclear Proteins; C101467:XRCC4 protein, human; D004247:DNA; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D011088:DNA Ligases; D000072481:DNA Ligase ATP