title: Mycobacterial Ku and ligase proteins constitute a two-component NHEJ repair machine.
abstract: In mammalian cells, repair of DNA double-strand breaks (DSBs) by nonhomologous end-joining (NHEJ) is critical for genome stability. Although the end-bridging and ligation steps of NHEJ have been reconstituted in vitro, little is known about the end-processing reactions that occur before ligation. Recently, functionally homologous end-bridging and ligation activities have been identified in prokarya. Consistent with its homology to polymerases and nucleases, we demonstrate that DNA ligase D from Mycobacterium tuberculosis (Mt-Lig) possesses a unique variety of nucleotidyl transferase activities, including gap-filling polymerase, terminal transferase, and primase, and is also a 3' to 5' exonuclease. These enzyme activities allow the Mt-Ku and Mt-Lig proteins to join incompatible DSB ends in vitro, as well as to reconstitute NHEJ in vivo in yeast. These results demonstrate that prokaryotic Ku and ligase form a bona fide NHEJ system that encodes all the recognition, processing, and ligation activities required for DSB repair.
authors.affiliation: Cambridge Institute for Medical Research, University of Cambridge, Department of Haematology, Hills Road, Cambridge CB2 2XY, UK.
authors.forename: Marina
authors.initials: M
authors.lastname: Della
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Palmbos
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Tseng
authors.forename: Louise M
authors.initials: LM
authors.lastname: Tonkin
authors.forename: James M
authors.initials: JM
authors.lastname: Daley
authors.forename: Leana M
authors.initials: LM
authors.lastname: Topper
authors.forename: Robert S
authors.initials: RS
authors.lastname: Pitcher
authors.forename: Alan E
authors.initials: AE
authors.lastname: Tomkinson
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Wilson
authors.forename: Aidan J
authors.initials: AJ
authors.lastname: Doherty
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D011088:DNA Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004254:DNA Nucleotidyltransferases / Q000737:chemistry / Q000378:metabolism; D019915:DNA Primase / Q000737:chemistry / Q000378:metabolism; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism; D005092:Exonucleases / Q000737:chemistry / Q000378:metabolism; D009154:Mutation; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004247:DNA; D004254:DNA Nucleotidyltransferases; D019915:DNA Primase; D004259:DNA-Directed DNA Polymerase; D005092:Exonucleases; D011088:DNA Ligases; C493173:DNA ligase D, Mycobacterium tuberculosis