title: ssDNA fragments induce cell senescence by telomere uncapping.
abstract: Telomere uncapping is known to induce senescence by activating a DNA damage response (DDR). However, it is still unclear what structural features of uncapped telomeres activate DDR. One hypothesis is that the exposure of the telomeric single-stranded G-rich 3' overhang triggers a DNA damage response and is, thus, equivalent to telomere uncapping. To mimic this, we compared the effects of two short single-stranded oligonucleotides, (TTAGGG)(2) and (CCCTAA)(2). G-rich oligonucleotides induced DNA damage foci containing gammaH2AX and senescence-like arrest, whilst C-rich oligonucleotides had no effect. Oligonucleotides did not co-localize with gammaEta2AlphaX foci, instead the induced DNA damage foci were preferentially localized at telomeres. BrdU incorporation assays showed that the effect of G oligonucleotides on gammaH2AX foci formation was cell cycle-dependent; entry of cells into S phase was necessary for subsequent DNA damage foci formation. Together, our results show that short G-rich single-stranded oligonucleotides induce telomere uncapping in a cell cycle-dependent manner, probably by titrating essential factors like Pot1 away from telomeres.
authors.affiliation: Centre for Integrated Systems Biology of Ageing and Nutrition, Institute for Ageing and Health, Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Avgi
authors.initials: A
authors.lastname: Tsolou
authors.forename: João F
authors.initials: JF
authors.lastname: Passos
authors.forename: Glyn
authors.initials: G
authors.lastname: Nelson
authors.forename: Yasumichi
authors.initials: Y
authors.lastname: Arai
authors.forename: Thomas von
authors.initials: Tv
authors.lastname: Zglinicki
mesh_terms: D002453:Cell Cycle / Q000235:genetics; D002478:Cells, Cultured; D016922:Cellular Senescence / Q000235:genetics / Q000502:physiology*; D004249:DNA Damage / Q000235:genetics / Q000502:physiology*; D004260:DNA Repair / Q000235:genetics; D004277:DNA, Single-Stranded / Q000235:genetics; D005347:Fibroblasts / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D042822:Genomic Instability; D006801:Humans; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism*; D000089804:Shelterin Complex; D016615:Telomere / Q000235:genetics / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000502:physiology*
chemical_list: D004277:DNA, Single-Stranded; D009841:Oligonucleotides; C440849:POT1 protein, human; D000089804:Shelterin Complex; D034501:Telomere-Binding Proteins