title: The Werner syndrome protein operates in base excision repair and cooperates with DNA polymerase beta.
abstract: Genome instability is a characteristic of cancer and aging, and is a hallmark of the premature aging disorder Werner syndrome (WS). Evidence suggests that the Werner syndrome protein (WRN) contributes to the maintenance of genome integrity through its involvement in DNA repair. In particular, biochemical evidence indicates a role for WRN in base excision repair (BER). We have previously reported that WRN helicase activity stimulates DNA polymerase beta (pol beta) strand displacement synthesis in vitro. In this report we demonstrate that WRN exonuclease activity can act cooperatively with pol beta, a polymerase lacking 3'-5' proofreading activity. Furthermore, using small interference RNA technology, we demonstrate that WRN knockdown cells are hypersensitive to the alkylating agent methyl methanesulfonate, which creates DNA damage that is primarily repaired by the BER pathway. In addition, repair assays using whole cell extracts from WRN knockdown cells indicate a defect in long patch (LP) BER. These findings demonstrate that WRN plays a direct role in the repair of methylation-induced DNA damage, and suggest a role for both WRN helicase and exonuclease activities together with pol beta during LP BER.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, NIH, Baltimore, MD, USA.
authors.forename: Jeanine A
authors.initials: JA
authors.lastname: Harrigan
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
authors.forename: Rajendra
authors.initials: R
authors.lastname: Prasad
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Opresko
authors.forename: Gad
authors.initials: G
authors.lastname: Beck
authors.forename: Alfred
authors.initials: A
authors.lastname: May
authors.forename: Samuel H
authors.initials: SH
authors.lastname: Wilson
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
mesh_terms: D000477:Alkylating Agents / Q000633:toxicity; D020137:Base Pair Mismatch; D002460:Cell Line; D004249:DNA Damage; D004265:DNA Helicases / Q000037:antagonists & inhibitors / Q000502:physiology*; D019951:DNA Polymerase beta / Q000378:metabolism*; D004260:DNA Repair; D005090:Exodeoxyribonucleases / Q000037:antagonists & inhibitors / Q000502:physiology*; D006801:Humans; D008741:Methyl Methanesulfonate / Q000633:toxicity; D034622:RNA Interference; D053484:RecQ Helicases; D000071657:Werner Syndrome Helicase
chemical_list: D000477:Alkylating Agents; D008741:Methyl Methanesulfonate; D019951:DNA Polymerase beta; D005090:Exodeoxyribonucleases; D004265:DNA Helicases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase