title: Efficient processing of abasic sites by bacterial nonhomologous end-joining Ku proteins.
abstract: Intracellular reactive oxygen species as well as the exposure to harsh environmental conditions can cause, in the single chromosome of Bacillus subtilis spores, the formation of apurinic/apyrimidinic (AP) sites and strand breaks whose repair during outgrowth is crucial to guarantee cell viability. Whereas double-stranded breaks are mended by the nonhomologous end joining (NHEJ) system composed of an ATP-dependent DNA Ligase D (LigD) and the DNA-end-binding protein Ku, repair of AP sites would rely on an AP endonuclease or an AP-lyase, a polymerase and a ligase. Here we show that B. subtilis Ku (BsuKu), along with its pivotal role in allowing joining of two broken ends by B. subtilis LigD (BsuLigD), is endowed with an AP/deoxyribose 5'-phosphate (5'-dRP)-lyase activity that can act on ssDNA, nicked molecules and DNA molecules without ends, suggesting a potential role in BER during spore outgrowth. Coordination with BsuLigD makes possible the efficient joining of DNA ends with near terminal abasic sites. The role of this new enzymatic activity of Ku and its potential importance in the NHEJ pathway is discussed. The presence of an AP-lyase activity also in the homolog protein from the distantly related bacterium Pseudomonas aeruginosa allows us to expand our results to other bacterial Ku proteins.
authors.affiliation: Instituto de Biología Molecular 'Eladio Viñuela' (CSIC), Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM). Nicolás Cabrera 1, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: de Ory
authors.affiliation: Instituto de Biología Molecular 'Eladio Viñuela' (CSIC), Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM). Nicolás Cabrera 1, Cantoblanco, 28049 Madrid, Spain.
authors.forename: Olga
authors.initials: O
authors.lastname: Zafra
authors.affiliation: Instituto de Biología Molecular 'Eladio Viñuela' (CSIC), Centro de Biología Molecular 'Severo Ochoa' (CSIC-UAM). Nicolás Cabrera 1, Cantoblanco, 28049 Madrid, Spain mdevega@cbm.csic.es.
authors.forename: Miguel
authors.initials: M
authors.lastname: de Vega
mesh_terms: D001412:Bacillus subtilis / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D059766:DNA End-Joining Repair; D011088:DNA Ligases / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019761:Phosphorus-Oxygen Lyases / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D004247:DNA; C423906:5'-deoxyribose phosphate lyase; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D019761:Phosphorus-Oxygen Lyases; D011088:DNA Ligases