title: Mutations of the Yku80 C terminus and Xrs2 FHA domain specifically block yeast nonhomologous end joining.
abstract: The nonhomologous end-joining (NHEJ) pathway of DNA double-strand break repair requires three protein complexes in Saccharomyces cerevisiae: MRX (Mre11-Rad50-Xrs2), Ku (Ku70-Ku80), and DNA ligase IV (Dnl4-Lif1-Nej1). Much is known about the interactions that mediate the formation of each complex, but little is known about how they act together during repair. A comprehensive yeast two-hybrid screen of the NHEJ factors of S. cerevisiae revealed all known interactions within the MRX, Ku, and DNA ligase IV complexes, as well as three additional, weaker interactions between Yku80-Dnl4, Xrs2-Lif1, and Mre11-Yku80. Individual and combined deletions of the Yku80 C terminus and the Xrs2 forkhead-associated (FHA) domain were designed based on the latter two-hybrid results. These deletions synergistically blocked NHEJ but not the telomere and recombination functions of Ku and MRX, confirming that these protein regions are functionally important specifically for NHEJ. Further mutational analysis of Yku80 identified a putative C-terminal amphipathic alpha-helix that is both required for its NHEJ function and strikingly similar to a DNA-dependent protein kinase interaction motif in human Ku80. These results identify a novel role in yeast NHEJ for the poorly characterized Ku80 C-terminal and Xrs2 FHA domains, and they suggest that redundant binding of DNA ligase IV facilitates completion of this DNA repair event.
authors.affiliation: Department of Pathology, University of Michigan Medical School, Ann Arbor, 48109-0602, USA.
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Palmbos
authors.forename: James M
authors.initials: JM
authors.lastname: Daley
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wilson
mesh_terms: D034961:Antigens, Nuclear / Q000378:metabolism; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism; D004252:DNA Mutational Analysis; D004260:DNA Repair; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004706:Endodeoxyribonucleases / Q000378:metabolism; D005090:Exodeoxyribonucleases / Q000378:metabolism; D000072200:Ku Autoantigen; D008969:Molecular Sequence Data; D009154:Mutation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion; D016615:Telomere / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: D034961:Antigens, Nuclear; D004271:DNA, Fungal; D004268:DNA-Binding Proteins; C000607891:DNL4 protein, S cerevisiae; C000607893:LIG4 protein, human; C086930:RAD50 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C086929:XRS2 protein, S cerevisiae; C520770:YKU80 protein, S cerevisiae; C081647:high affinity DNA-binding factor, S cerevisiae; D004706:Endodeoxyribonucleases; D005090:Exodeoxyribonucleases; C094191:MRE11 protein, S cerevisiae; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen; D011088:DNA Ligases; D000072481:DNA Ligase ATP