Figure 3: Growth suppression induced by SWNT-COOH associates with the production of DNA-damage response.

(a) Proliferation curves of HeLa and K562 cells treated with 2′-O-MeRNA, SWNT-COOH (25 and 50 μg ml⁻¹, respectively.) or transfected with TRF2^ΔBΔM At the indicated times, cells were counted and the population doublings (PDs) were determined. (b) Western blot analysis of γ-H2AX in K562 and HeLa cells treated with 2′-O-MeRNA, SWNT-COOH (50 μg ml⁻¹) or transfected with TRF2^ΔBΔM for 2 weeks. The levels of H2AX were used as loading control. (c) Percentage of cells containing γ-H2AX and 53BP1 foci in K562 and HeLa cells treated with 2′-O-MeRNA, SWNT-COOH (50 μg ml⁻¹) or transfected with TRF2^ΔBΔM for 2 weeks. γ-H2AX and 53BP1 foci were quantified using mouse monoclonal antibodies. On average, more than 200 cells were screened in three independent experiments. Error bars indicate s.d. **P<0.001, two-tailed Student's t-test. (d) Representative immunofluorescence images of γ-H2AX and 53BP1 foci in HeLa cells treated with 2′-O-MeRNA, SWNT-COOH (50 μg ml⁻¹) or transfected with TRF2^ΔBΔM for 2 weeks. Scale bar equals 20 μM.