Interaction of telomestatin with the telomeric single-strand overhang.
The extremities of chromosomes end in a G-rich single-stranded overhang that has been implicated in the onset of the replicative senescence. The repeated sequence forming a G-overhang is able to adopt a peculiar four-stranded DNA structure in vitro called a G-quadruplex, which is a poor substrate for telomerase. Small molecule ligands that selectively stabilize the telomeric G-quadruplex induce telomere shortening and a delayed growth arrest. Here we show that the G-quadruplex ligand telomestatin has a dramatic effect on the conformation of intracellular G-overhangs. Competition experiments indicate that telomestatin strongly binds in vitro and in vivo to the telomeric overhang and impairs its single-stranded conformation. Long-term treatment of cells with telomestatin greatly reduces the G-overhang size, as evidenced by specific hybridization or telomeric oligonucleotide ligation assay experiments, with a concomitant delayed loss of cell viability. In vivo protection experiments using dimethyl sulfate also indicate that telomestatin treatment alters the dimethyl sulfate effect on G-overhangs, a result compatible with the formation of a local quadruplex structure at telomeric overhang. Altogether these experiments strongly support the hypothesis that the telomeric G-overhang is an intracellular target for the action of telomestatin.
Laboratoire d'Onco-Pharmacologie, JE 2428, UFR de Pharmacie, Université de Reims Champagne Ardenne, 51 rue Cognacq-Jay, 51096 Reims, France.
Dennis
D
Gomez
Rajaa
R
Paterski
Thibault
T
Lemarteleur
Kazuo
K
Shin-Ya
Jean-Louis
JL
Mergny
Jean-François
JF
Riou
D001483:Base Sequence; D001667:Binding, Competitive; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004247:DNA; D004277:DNA, Single-Stranded; D054856:G-Quadruplexes; D006801:Humans; D009690:Nucleic Acid Conformation / Q000187:drug effects; D010080:Oxazoles / Q000494:pharmacology*; D013463:Sulfuric Acid Esters / Q000494:pharmacology; D016615:Telomere / Q000737:chemistry* / Q000187:drug effects
D004277:DNA, Single-Stranded; D010080:Oxazoles; D013463:Sulfuric Acid Esters; C431888:telomestatin; D004247:DNA; C007482:dimethyl sulfate