title: The G-quadruplex ligand telomestatin impairs binding of topoisomerase IIIalpha to G-quadruplex-forming oligonucleotides and uncaps telomeres in ALT cells.
abstract: In Alternative Lengthening of Telomeres (ALT) cell lines, specific nuclear bodies called APBs (ALT-associated PML bodies) concentrate telomeric DNA, shelterin components and recombination factors associated with telomere recombination. Topoisomerase IIIalpha (Topo III) is an essential telomeric-associated factor in ALT cells. We show here that the binding of Topo III to telomeric G-overhang is modulated by G-quadruplex formation. Topo III binding to G-quadruplex-forming oligonucleotides was strongly inhibited by telomestatin, a potent and specific G-quadruplex ligand. In ALT cells, telomestatin treatment resulted in the depletion of the Topo III/BLM/TRF2 complex and the disruption of APBs and led to the segregation of PML, shelterin components and Topo III. Interestingly, a DNA damage response was observed at telomeres in telomestatin-treated cells. These data indicate the importance of G-quadruplex stabilization during telomere maintenance in ALT cells. The function of TRF2/Topo III/BLM in the resolution of replication intermediates at telomeres is discussed.
authors.affiliation: Laboratoire d'Onco-Pharmacologie, JE 2428, UFR de Pharmacie, Université de Reims Champagne-Ardenne, Reims, France.
authors.forename: Nassima
authors.initials: N
authors.lastname: Temime-Smaali
authors.forename: Lionel
authors.initials: L
authors.lastname: Guittat
authors.forename: Assitan
authors.initials: A
authors.lastname: Sidibe
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shin-ya
authors.forename: Chantal
authors.initials: C
authors.lastname: Trentesaux
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Riou
mesh_terms: D002467:Cell Nucleus / Q000378:metabolism; D002469:Cell Separation; D002478:Cells, Cultured; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D005434:Flow Cytometry; D054856:G-Quadruplexes; D006801:Humans; D008024:Ligands; D008954:Models, Biological; D009841:Oligonucleotides / Q000737:chemistry*; D010080:Oxazoles / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D016615:Telomere / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D008024:Ligands; D009841:Oligonucleotides; D010080:Oxazoles; C431888:telomestatin; D004264:DNA Topoisomerases, Type I