title: Specific interaction of IP6 with human Ku70/80, the DNA-binding subunit of DNA-PK.
abstract: In eukaryotic cells, DNA double-strand breaks can be repaired by non-homologous end-joining, a process dependent upon Ku70/80, XRCC4 and DNA ligase IV. In mammals, this process also requires DNA-PK(cs), the catalytic subunit of the DNA-dependent protein kinase DNA-PK. Previously, inositol hexakisphosphate (IP6) was shown to be bound by DNA-PK and to stimulate DNA-PK-dependent end-joining in vitro. Here, we localize IP6 binding to the Ku70/80 subunits of DNA- PK, and show that DNA-PK(cs) alone exhibits no detectable affinity for IP6. Moreover, proteolysis mapping of Ku70/80 in the presence and absence of IP6 indicates that binding alters the conformation of the Ku70/80 heterodimer. The yeast homologue of Ku70/80, yKu70/80, fails to bind IP6, indicating that the function of IP6 in non-homologous end-joining, like that of DNA-PK(cs), is unique to the mammalian end-joining process.
authors.affiliation: Cancer Research UK, London Research Institute, Clare Hall Laboratories, South Mimms, Hertfordshire EN6 3LD, UK.
authors.forename: Les A
authors.initials: LA
authors.lastname: Hanakahi
authors.forename: Stephen C
authors.initials: SC
authors.lastname: West
mesh_terms: D034961:Antigens, Nuclear; D001665:Binding Sites; D004265:DNA Helicases; D051747:DNA-Activated Protein Kinase; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010833:Phytic Acid / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C520769:YKU70 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; D010833:Phytic Acid; D051747:DNA-Activated Protein Kinase; C497263:PRKDC protein, human; D017346:Protein Serine-Threonine Kinases; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen