Preferential binding of a G-quadruplex ligand to human chromosome ends.
The G-overhangs of telomeres are thought to adopt particular conformations, such as T-loops or G-quadruplexes. It has been suggested that G-quadruplex structures could be stabilized by specific ligands in a new approach to cancer treatment consisting in inhibition of telomerase, an enzyme involved in telomere maintenance and cell immortality. Although the formation of G-quadruplexes was demonstrated in vitro many years ago, it has not been definitively demonstrated in living human cells. We therefore investigated the chromosomal binding of a tritiated G-quadruplex ligand, 3H-360A (2,6-N,N'-methyl-quinolinio-3-yl)-pyridine dicarboxamide [methyl-3H]. We verified the in vitro selectivity of 3H-360A for G-quadruplex structures by equilibrium dialysis. We then showed by binding experiments with human genomic DNA that 3H-360A has a very potent selectivity toward G-quadruplex structures of the telomeric 3'-overhang. Finally, we performed autoradiography of metaphase spreads from cells cultured with 3H-360A. We found that 3H-360A was preferentially bound to chromosome terminal regions of both human normal (peripheral blood lymphocytes) and tumor cells (T98G and CEM1301). In conclusion, our results provide evidence that a specific G-quadruplex ligand interacts with the terminal ends of human chromosomes. They support the hypothesis that G-quadruplex ligands induce and/or stabilize G-quadruplex structures at telomeres of human cells.
Granotier
Christine
C
LRP, DRR, CEA 92265, Fontenay-aux-Roses, France.
Pennarun
Gaëlle
G
Riou
Lydia
L
Hoffschir
Françoise
F
Gauthier
Laurent R
LR
De Cian
Anne
A
Gomez
Dennis
D
Mandine
Eliane
E
Riou
Jean-François
JF
Mergny
Jean-Louis
JL
Mailliet
Patrick
P
Dutrillaux
Bernard
B
Boussin
François D
FD
D001665:Binding Sites; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002877:Chromosomes, Human / Q000737:chemistry* / Q000378:metabolism; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D054856:G-Quadruplexes; D006147:Guanine / Q000737:chemistry; D006801:Humans; D008024:Ligands; D008214:Lymphocytes / Q000648:ultrastructure; D008677:Metaphase; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism*; D011804:Quinolines / Q000737:chemistry / Q000378:metabolism*; D016615:Telomere / Q000737:chemistry* / Q000378:metabolism
C502660:2,6-N,N'-methyl-quinolinio-3-yl-pyridine dicarboxamide; D008024:Ligands; D011725:Pyridines; D011804:Quinolines; D006147:Guanine; D004247:DNA