title: Involvement of DNA polymerase beta in protection against the cytotoxicity of oxidative DNA damage.
abstract: We had shown previously that DNA polymerase beta (beta-pol) null mouse fibroblasts, deficient in base excision repair (BER), are hypersensitive to monofunctional methylating agents but not to hydrogen peroxide (H2O2). This is surprising because beta-pol is thought to be involved in BER of oxidative as well as methylated DNA damage. We confirm these findings here in early-passage cells. However, with time in culture, beta-pol null cells become hypersensitive to H2O2 and other reactive oxygen species-generating agents. Analysis of in vitro BER reveals a strong deficiency in single-nucleotide BER of 8-oxoguanine (8-oxoG) by both early- and late-passage beta-pol null cell extracts. Therefore, in early-passage wild-type and beta-pol null cells, the capacity for single-nucleotide BER of 8-oxoG does not correlate with cellular sensitivity to H2O2. Expression of beta-pol protein in the late-passage null cells almost completely reverses the H2O2-hypersensitivity phenotype. Methoxyamine (MX) treatment sensitizes late-passage wild-type cells to H2O2 as expected for beta-pol-mediated single-nucleotide BER; however in beta-pol null cells, MX has no effect. The data indicate a role(s) of beta-pol-dependent repair in protection against the cytotoxicity of oxidative DNA damage in wild-type cells.
authors.affiliation: Laboratory of Structural Biology, NIEHS, National Institutes of Health, Research Triangle Park, NC 27709, USA.
authors.forename: Julie K
authors.initials: JK
authors.lastname: Horton
authors.forename: Audrey
authors.initials: A
authors.lastname: Baker
authors.forename: Brian J Vande
authors.initials: BJ
authors.lastname: Berg
authors.forename: Robert W
authors.initials: RW
authors.lastname: Sobol
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000633:toxicity; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D019610:Cytoprotection / Q000502:physiology; D004249:DNA Damage / Q000187:drug effects*; D019951:DNA Polymerase beta / Q000235:genetics / Q000502:physiology*; D017931:DNA Primers / Q000737:chemistry; D004260:DNA Repair; D043382:DNA-Formamidopyrimidine Glycosylase; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology*; D005978:Glutathione / Q000172:deficiency / Q000378:metabolism; D006151:Guanosine / Q000031:analogs & derivatives* / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000633:toxicity; D006898:Hydroxylamines / Q000633:toxicity; D066298:In Vitro Techniques; D051379:Mice; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D016877:Oxidants / Q000633:toxicity*; D030421:Peroxynitrous Acid / Q000633:toxicity; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000187:drug effects; D014162:Transfection
chemical_list: D000970:Antineoplastic Agents; D017931:DNA Primers; D006898:Hydroxylamines; D016877:Oxidants; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D006151:Guanosine; D030421:Peroxynitrous Acid; C046215:8-hydroxyguanosine; C005214:methoxyamine; D006861:Hydrogen Peroxide; D011065:Poly(ADP-ribose) Polymerases; D019951:DNA Polymerase beta; D009699:N-Glycosyl Hydrolases; D043382:DNA-Formamidopyrimidine Glycosylase; D005978:Glutathione