title: Association of DNA polymerase mu (pol mu) with Ku and ligase IV: role for pol mu in end-joining double-strand break repair.
abstract: Mammalian DNA polymerase mu (pol mu) is related to terminal deoxynucleotidyl transferase, but its biological role is not yet clear. We show here that after exposure of cells to ionizing radiation (IR), levels of pol mu protein increase. pol mu also forms discrete nuclear foci after IR, and these foci are largely coincident with IR-induced foci of gammaH2AX, a previously characterized marker of sites of DNA double-strand breaks. pol mu is thus part of the cellular response to DNA double-strand breaks. pol mu also associates in cell extracts with the nonhomologous end-joining repair factor Ku and requires both Ku and another end-joining factor, XRCC4-ligase IV, to form a stable complex on DNA in vitro. pol mu in turn facilitates both stable recruitment of XRCC4-ligase IV to Ku-bound DNA and ligase IV-dependent end joining. In contrast, the related mammalian DNA polymerase beta does not form a complex with Ku and XRCC4-ligase IV and is less effective than pol mu in facilitating joining mediated by these factors. Our data thus support an important role for pol mu in the end-joining pathway for repair of double-strand breaks.
authors.affiliation: Lineberger Comprehensive Cancer Center, Mason Farm Road, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7295, USA.
authors.forename: Kiran N
authors.initials: KN
authors.lastname: Mahajan
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Nick McElhinny
authors.forename: Beverly S
authors.initials: BS
authors.lastname: Mitchell
authors.forename: Dale A
authors.initials: DA
authors.lastname: Ramsden
mesh_terms: D034961:Antigens, Nuclear; D002460:Cell Line; D004249:DNA Damage; D004265:DNA Helicases; D019951:DNA Polymerase beta / Q000378:metabolism; D004260:DNA Repair / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D000072200:Ku Autoantigen; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C101467:XRCC4 protein, human; C407743:DNA polymerase mu; D019951:DNA Polymerase beta; D004259:DNA-Directed DNA Polymerase; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen