title: Differential cleavage of oligonucleotides containing the benzene-derived adduct, 1,N6-benzetheno-dA, by the major human AP endonuclease HAP1 and Escherichia coli exonuclease III and endonuclease IV.
abstract: We report here that the newly synthesized DNA adduct, 1,N6-benzetheno-dA (pBQ-dA), in defined oligonucleotides [Chenna and Singer, Chem. Res. Toxicol., 8, 865-874], is a substrate for the major human AP endonuclease, HAP1, and the Escherichia coli AP endonucleases, exonuclease III and endonuclease IV. The mechanism of cleavage is identical to that reported previously for 3,N4-benzetheno-dC (pBQ-dC) and leads to a phosphodiester bond cleavage 5' to the adduct. There are, however, significant differences in the rate of cleavage of this adduct by these enzymes. The two bacterial AP endonucleases are both much more efficient than the human repair enzyme. In addition, using two random oligodeoxynucleotide sequences containing a single pBQ-dA, exonuclease III and endonuclease IV are similarly active, while HAP1 shows a distinct sequence preference of approximately 10-fold in efficiency of cleavage. The repair of this adduct by the three recombinant enzymes is further confirmed by using both active site mutant HAP1 proteins and by E.coli mutant strains lacking exonuclease III and/ or endonuclease IV. This sequence-dependent repair of pBQ-dA by HAP1 may play an important role in modulating benzene-induced carcinogenesis.
authors.affiliation: Donner Laboratory, Lawrence Berkeley National Laboratory, University of California, Berkeley 94720, USA.
authors.forename: B
authors.initials: B
authors.lastname: Hang
authors.forename: A
authors.initials: A
authors.lastname: Chenna
authors.forename: J
authors.initials: J
authors.lastname: Sági
authors.forename: B
authors.initials: B
authors.lastname: Singer
mesh_terms: D001562:Benzimidazoles / Q000378:metabolism*; D019757:Carbon-Oxygen Lyases / Q000378:metabolism*; D018736:DNA Adducts / Q000378:metabolism*; D004260:DNA Repair; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D003839:Deoxyadenosines / Q000378:metabolism*; D003841:Deoxycytidine / Q000031:analogs & derivatives / Q000378:metabolism; D043223:Deoxyribonuclease IV (Phage T4-Induced); D029968:Escherichia coli Proteins; D005090:Exodeoxyribonucleases / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: C096961:3-hydroxy-1,N(4)-benzetheno-2'-deoxycytidine; C096962:9-hydroxy-1,N(6)-benzetheno-2'-deoxyadenosine; D001562:Benzimidazoles; D018736:DNA Adducts; D003839:Deoxyadenosines; D029968:Escherichia coli Proteins; D009687:Nuclear Proteins; D003841:Deoxycytidine; D005090:Exodeoxyribonucleases; C020133:exodeoxyribonuclease III; D043223:Deoxyribonuclease IV (Phage T4-Induced); C468972:endonuclease IV, E coli; D019757:Carbon-Oxygen Lyases; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase