Figure 5: Telomere uncapping induced by carboxylated SWNTs.

(a) Representative images of anaphase bridges and micronuclei in HeLa cells treated for 6 days with carboxylated SWNTs (50 μg ml⁻¹) or transfected with TRF2^ΔBΔM were shown. Cells were stained with DAPI and images were recorded. Red arrow indicated bridge formation, and green arrow indicated micronuclei formation. Anaphase bridges and micronuclei often co-existed in treated cells. Scale bar equals 10 μM. (b) Telomere fusion induced by carboxylated SWNTs or transfection with TRF2^ΔBΔM metaphase spreads were stained with DAPI or Giemsa, respectively. Scale bar equals 10 μM. (c) The frequency of telomere instability was calculated as the ratio between cells exhibiting anaphase bridges/micronuclei and the total number of anaphase cells (at least 50 anaphase cells were examined). Telomeric fusion frequency was calculated as total number of telomeric fusions/total number of metaphases. The data represented the means of four independent experiments with s.d. **P<0.001. (d) SWNT-COOH induced accessible telomere ends. TRF1 (green) were used to detect telomeres, whereas TdT-cy3 (red) was used as a marker of uncapped telomeres in HeLa cells treated with carboxylated SWNTs, 2′-O-MeRNA or transfection with TRF2^ΔBΔM merged signals were shown in the right. Scale bar equals 5 μM. (e) Quantification of the percentage of TdT-cy3-positive cells in SWNT-COOH, 2′-O-MeRNA or TRF2^ΔBΔM-treated cells. (f) Quantification of the percentage of colocalization of telomeric signals with TdT-cy3 signals in SWNT-COOH, 2′-O-MeRNA or TRF2^ΔBΔM-treated cells. In panels e and f, a minimum of 100 nuclei was scored, and error bars represented s.d. **P<0.001.