A novel small molecule that alters shelterin integrity and triggers a DNA-damage response at telomeres

Abstract

We describe a novel synthetic small molecule which shows an unprecedented stabilization of the human telomeric G-quadruplex with high selectivity relative to double-stranded DNA. We report that this compound can be used in vitro to inhibit telomerase activity and to uncap human POT1 (protection of telomeres 1) from the telomeric G-overhang. We also show that the small molecule G-quadruplex binder induces a partial alteration of shelterin through POT1 uncapping from telomeres in human HT1080 cancer cells and the presence of gammaH2AX foci colocalized at telomeres.

Figure 1

(a) The six-protein complex shelterin bound to telomeric DNA; (b) structure of 1.

Figure 2

POT1 uncapping: inhibition of POT1 binding to the telomeric sequence dG₃(T₂AG₃)₇ induced by 1 in vitro.

Figure 3

Effect of 1 on HT1080GFP-POT1 cells: (a) Untreated control, fluorescent GFP-POT1 (green); (b) after treatment with 1 (1 μM) for 72 h; (c) γH2AX foci in cells treated with 1 (3 μM) for 24 h (red); (d) colocalization of γH2AX foci (red) and GFP-POT1 (green) at telomeres (marked with arrowheads). DAPI DNA staining (blue) throughout.