title: A role for WRN in telomere-based DNA damage responses.
abstract: Telomeres cap the ends of eukaryotic chromosomes and prevent them from being recognized as DNA breaks. We have shown that certain DNA damage responses induced during senescence and, at times of telomere uncapping, also can be induced by treatment of cells with small DNA oligonucleotides homologous to the telomere 3' single-strand overhang (T-oligos), implicating this overhang in generation of these telomere-based damage responses. Here, we show that T-oligo-treated fibroblasts contain gammaH2AX foci and that these foci colocalize with telomeres. T-oligos with nuclease-resistant 3' ends are inactive, suggesting that a nuclease initiates T-oligo responses. We therefore examined WRN, a 3'-->5' exonuclease and helicase mutated in Werner syndrome, a disorder characterized by aberrant telomere maintenance, premature aging, chromosomal rearrangements, and predisposition to malignancy. Normal fibroblasts and U20S osteosarcoma cells rendered deficient in WRN showed reduced phosphorylation of p53 and histone H2AX in response to T-oligo treatment. Together, these data demonstrate a role for WRN in processing of telomeric DNA and subsequent activation of DNA damage responses. The T-oligo model helps define the role of WRN in telomere maintenance and initiation of DNA damage responses after telomere disruption.
authors.affiliation: Department of Dermatology, Boston University School of Medicine, 609 Albany Street, Boston, MA 02118, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Eller
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Liao
authors.forename: SuiYang
authors.initials: S
authors.lastname: Liu
authors.forename: Kendra
authors.initials: K
authors.lastname: Hanna
authors.forename: Helena
authors.initials: H
authors.lastname: Bäckvall
authors.forename: Patricia L
authors.initials: PL
authors.lastname: Opresko
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Gilchrest
mesh_terms: D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics; D004249:DNA Damage; D004260:DNA Repair; D005090:Exodeoxyribonucleases; D006801:Humans; D007231:Infant, Newborn; D009838:Oligodeoxyribonucleotides / Q000494:pharmacology; D053484:RecQ Helicases / Q000235:genetics / Q000502:physiology*; D016615:Telomere / Q000235:genetics*; D014898:Werner Syndrome / Q000235:genetics* / Q000473:pathology; D000071657:Werner Syndrome Helicase
chemical_list: D009838:Oligodeoxyribonucleotides; C027903:oligo (dT); D005090:Exodeoxyribonucleases; D053484:RecQ Helicases; C098785:WRN protein, human; D000071657:Werner Syndrome Helicase