title: Evolutionary and functional conservation of the DNA non-homologous end-joining protein, XLF/Cernunnos.
abstract: Non-homologous end-joining is a major pathway of DNA double-strand break repair in mammalian cells, deficiency in which confers radiosensitivity and immune deficiency at the whole organism level. A core protein complex comprising the Ku70/80 heterodimer together with a complex between DNA ligase IV and XRCC4 is conserved throughout eukaryotes and assembles at double-strand breaks to mediate ligation of broken DNA ends. In Saccharomyces cerevisiae an additional NHEJ protein, Nej1p, physically interacts with the ligase IV complex and is required in vivo for ligation of DNA double-strand breaks. Recent studies with cells derived from radiosensitive and immune-deficient patients have identified the human protein, XLF (also named Cernunnos), as a crucial NHEJ protein. Here we show that XLF and Nej1p are members of the same protein superfamily and that this family has members in diverse eukaryotes. Indeed, we show that a member of this family encoded by a previously uncharacterized open-reading frame in the Schizosaccharomyces pombe genome is required for NHEJ in this organism. Furthermore, our data reveal that XLF family proteins can bind to DNA and directly interact with the ligase IV-XRCC4 complex to promote DSB ligation. We therefore conclude that XLF family proteins interact with the ligase IV-XRCC4 complex to constitute the evolutionarily conserved enzymatic core of the NHEJ machinery.
authors.affiliation: Genome Damage and Stability Centre, University of Sussex, Brighton BN1 9RQ, United Kingdom.
authors.forename: Pierre
authors.initials: P
authors.lastname: Hentges
authors.forename: Peter
authors.initials: P
authors.lastname: Ahnesorg
authors.forename: Robert S
authors.initials: RS
authors.lastname: Pitcher
authors.forename: Chris K
authors.initials: CK
authors.lastname: Bruce
authors.forename: Boris
authors.initials: B
authors.lastname: Kysela
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Green
authors.forename: Julie
authors.initials: J
authors.lastname: Bianchi
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wilson
authors.forename: Stephen P
authors.initials: SP
authors.lastname: Jackson
authors.forename: Aidan J
authors.initials: AJ
authors.lastname: Doherty
mesh_terms: D004247:DNA / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes; D004271:DNA, Fungal / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D006801:Humans; D066298:In Vitro Techniques; D046912:Multiprotein Complexes; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015003:Yeasts / Q000235:genetics / Q000378:metabolism
chemical_list: D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046912:Multiprotein Complexes; C508551:NHEJ1 protein, human; D029702:Schizosaccharomyces pombe Proteins; D004247:DNA; D045643:DNA Repair Enzymes