title: WRN exonuclease activity is blocked by DNA termini harboring 3' obstructive groups.
abstract: Reactive oxygen species, generated either by cellular respiration or upon exposure to environmental agents such as ionizing radiation (IR), attack DNA to form a variety of oxidized base and sugar modifications. Accumulation of oxidative DNA damage has been associated with age-related disease as well as the aging process. Single-strand breaks harboring oxidative 3' obstructive termini, e.g. 3' phosphates and 3' phosphoglycolates, must be removed prior to DNA repair synthesis or ligation. In addition, 3' tyrosyl-linked protein damage, resulting from therapeutic agents such as camptothecin (CPT), must be processed to initiate repair. Several nucleases participate in DNA repair and the excision of 3' obstructive ends. As the protein defective in the segmental progeroid Werner syndrome (WRN) possesses 3'-5' exonuclease activity, and Werner syndrome cells are hypersensitive to IR and CPT, we examined for WRN exonuclease activity on 3' blocking lesions. Moreover, we compared side-by-side the activity of four prominent human 3'-5' exonucleases (WRN, APE1, TREX1, and p53) on substrates containing 3' phosphates, phosphoglycolates, and tyrosyl residues. Our studies reveal that while WRN degrades 3' hydroxyl containing substrates in a non-processive manner, it does not excise 3' phosphate, phosphoglycolate, or tyrosyl groups. In addition, we found that APE1 was most active at excising 3' blocking termini in comparison to the disease-related exonucleases TREX1, WRN, and p53 under identical physiological reaction conditions, and that TREX1 was the most powerful 3'-5' exonuclease on undamaged oligonucleotide substrates.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, United States.
authors.forename: Jeanine A
authors.initials: JA
authors.lastname: Harrigan
authors.forename: Jinshui
authors.initials: J
authors.lastname: Fan
authors.forename: Jamil
authors.initials: J
authors.lastname: Momand
authors.forename: Fred W
authors.initials: FW
authors.lastname: Perrino
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
mesh_terms: D002478:Cells, Cultured; D004247:DNA / Q000737:chemistry* / Q000494:pharmacology*; D004260:DNA Repair / Q000502:physiology; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase / Q000037:antagonists & inhibitors / Q000235:genetics; D005090:Exodeoxyribonucleases; D016158:Genes, p53 / Q000235:genetics; D006016:Glycolates / Q000494:pharmacology; D006801:Humans; D009841:Oligonucleotides / Q000494:pharmacology; D010084:Oxidation-Reduction; D011506:Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D017382:Reactive Oxygen Species; D053484:RecQ Helicases / Q000037:antagonists & inhibitors* / Q000235:genetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D014443:Tyrosine / Q000737:chemistry; D000071657:Werner Syndrome Helicase
chemical_list: D006016:Glycolates; D009841:Oligonucleotides; D011506:Proteins; D017382:Reactive Oxygen Species; D011994:Recombinant Proteins; D014443:Tyrosine; D004247:DNA; D005090:Exodeoxyribonucleases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase; C085108:APEX1 protein, human; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; C013193:phosphoglycolate