title: The Werner syndrome protein functions in repair of Cr(VI)-induced replication-associated DNA damage.
abstract: Werner syndrome is a premature aging disorder characterized by cancer predisposition that is caused by loss of the Werner syndrome protein (WRN) helicase/exonuclease DNA repair protein. Hexavalent chromium is an environmental carcinogen and genotoxicant that is associated with respiratory cancers and induces several forms of DNA damage, including lesions that interfere with DNA replication. Based on the evidence that WRN protein facilitates repair of stalled and collapsed replication forks, we hypothesized that WRN functions in the cellular response to and recovery from Cr(VI)-induced genotoxicity and genomic instability. Here we report that human cells deficient in WRN protein are hypersensitive to Cr(VI) toxicity, and exhibit a delayed reduction in DNA breaks and stalled replication forks, indicated by gammaH2AX foci, during recovery from Cr(VI) exposure. Cr(VI)-induced WRN protein translocation from the nucleoli into nucleoplasmic foci in S-phase cells, and these foci colocalized with gammaH2AX foci indicating WRN responds to replication-associated DNA damage. As further evidence that Cr(VI) triggers stalled DNA replication, we observed Cr(VI) treatment induced an accumulation of cells in S-phase that exhibited high levels of gammaH2AX foci. Therefore, these data demonstrate a novel role for WRN protein in cellular protection against the environmental genotoxicant Cr(VI) and further provide evidence that Cr(VI) induces DNA replicative stress which has implications for aging and cancer.
authors.affiliation: Department of Environmental and Occupational Health, University of Pittsburgh Graduate School of Public Health, Pittsburgh, Pennsylvania 15219, USA.
authors.forename: Fu-Jun
authors.initials: FJ
authors.lastname: Liu
authors.forename: Aaron
authors.initials: A
authors.lastname: Barchowsky
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Opresko
mesh_terms: D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000187:drug effects* / Q000201:enzymology; D049109:Cell Proliferation / Q000187:drug effects; D053960:DNA Breaks; D004261:DNA Replication / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005090:Exodeoxyribonucleases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D006657:Histones / Q000378:metabolism; D006801:Humans; D007700:Kinetics; D009153:Mutagens / Q000633:toxicity*; D011192:Potassium Dichromate / Q000633:toxicity*; D021381:Protein Transport; D034622:RNA Interference; D053484:RecQ Helicases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D000071657:Werner Syndrome Helicase
chemical_list: C468783:H2AX protein, human; D006657:Histones; D009153:Mutagens; D005090:Exodeoxyribonucleases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase; D011192:Potassium Dichromate