title: Role for DNA polymerase beta in response to ionizing radiation.
abstract: Evidence for a role of DNA polymerase beta in determining radiosensitivity is conflicting. In vitro assays show an involvement of DNA polymerase beta in single strand break repair and base excision repair of oxidative damages, both products of ionizing radiation. Nevertheless the lack of DNA polymerase beta has been shown to have no effect on radiosensitivity. Here we show that mouse embryonic fibroblasts deficient in DNA polymerase beta are considerably more sensitive to ionizing radiation than wild-type cells, but only when confluent. The inhibitor methoxyamine renders abasic sites refractory to the dRP lyase activity of DNA polymerase beta. Methoxyamine did not significantly change radiosensitivity of wild-type fibroblasts in log phase. However, DNA polymerase beta deficient cells in log phase were radiosensitized by methoxyamine. Alkaline comet assays confirmed repair inhibition of ionizing radiation induced damage by methoxyamine in these cells, indicating both the existence of a polymerase beta-dependent long patch pathway and the involvement of another methoxyamine sensitive process, implying the participation of a second short patch polymerase(s) other than DNA polymerase beta. This is the first evidence of a role for DNA polymerase beta in radiosensitivity in vivo.
authors.affiliation: Division of Experimental Therapy, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands.
authors.forename: Christie
authors.initials: C
authors.lastname: Vermeulen
authors.forename: Manon
authors.initials: M
authors.lastname: Verwijs-Janssen
authors.forename: Patricia
authors.initials: P
authors.lastname: Cramers
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Begg
authors.forename: Conchita
authors.initials: C
authors.lastname: Vens
mesh_terms: D000818:Animals; D002453:Cell Cycle; D002460:Cell Line; D002470:Cell Survival / Q000528:radiation effects; D003114:Colony-Forming Units Assay; D004249:DNA Damage; D019951:DNA Polymerase beta / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000187:drug effects / Q000502:physiology*; D006898:Hydroxylamines / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D011836:Radiation Tolerance / Q000187:drug effects / Q000502:physiology*
chemical_list: D006898:Hydroxylamines; C005214:methoxyamine; D019951:DNA Polymerase beta