title: Ku antigen displays the AP lyase activity on a certain type of duplex DNA.
abstract: In the search for proteins reactive to apurinic/apyrimidinic (AP) sites, it has been earlier found that proteins of human cell extracts formed the Schiff-base-dependent covalent adduct with an apparent molecular mass of 100kDa with a partial DNA duplex containing an AP site and 5'- and 3'-protruding ends (DDE-AP DNA). The adduct of such electrophoretic mobility was characteristic of only DDE-AP DNA (Ilina et al., Biochem. Biophys. Acta 1784 (2008) 1777-1785). The protein in this unusual adduct was identified as the Ku80 subunit of Ku antigen by peptide mass mapping based on MALDI-TOF MS data (Kosova et al., Biopolym. Cell 30 (2014) 42-46). Here we studied the interaction of Ku with DDE-AP DNA in details. Purified Ku (the Ku80 subunit) was shown to form the 100-kDa adduct highly specific for AP DNA with a certain length of protruding ends, base opposite the AP site and AP site location. Ku is capable of AP site cleavage in DDE-AP DNA unlike in analogous AP DNA with blunt ends. Ku cleaves AP sites via β-elimination and prefers apurinic sites over apyrimidinic ones. The AP site in DDE-DNA can be repaired in an apurinic/apyrimidinic endonuclease-independent manner via the successive action of Ku (cleavage of the AP site), tyrosyl-DNA phosphodiesterase 1 (removal of the 3'-deoxyribose residue), polynucleotide kinase 3'-phosphatase (removal of the 3'-phosphate), DNA polymerase β (incorporation of dNMP), and DNA ligase (sealing the nick). These results provide a new insight into the role of Ku in the repair of AP sites.
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.
authors.forename: Anastasiya A
authors.initials: AA
authors.lastname: Kosova
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia.
authors.forename: Svetlana N
authors.initials: SN
authors.lastname: Khodyreva
authors.affiliation: Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia; Novosibirsk State University, Novosibirsk, Russia. Electronic address: lavrik@niboch.nsc.ru.
authors.forename: Olga I
authors.initials: OI
authors.lastname: Lavrik
mesh_terms: D001483:Base Sequence; D004247:DNA / Q000235:genetics / Q000378:metabolism*; D018736:DNA Adducts / Q000235:genetics / Q000378:metabolism*; D053903:DNA Breaks, Double-Stranded; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism; D019951:DNA Polymerase beta / Q000235:genetics / Q000378:metabolism; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D000072200:Ku Autoantigen / Q000235:genetics / Q000378:metabolism*; D008970:Molecular Weight; D010727:Phosphoric Diester Hydrolases / Q000235:genetics / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism
chemical_list: D018736:DNA Adducts; D021122:Protein Subunits; D004247:DNA; C530380:PNKP protein, human; D017853:Phosphotransferases (Alcohol Group Acceptor); D019951:DNA Polymerase beta; D010727:Phosphoric Diester Hydrolases; C122147:tyrosyl-DNA phosphodiesterase; D000072200:Ku Autoantigen; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D011088:DNA Ligases; D045643:DNA Repair Enzymes
keywords: AP lyase; AP sites; DNA repair; Ku antigen; Schiff base