Telomestatin Uncaps Telomeres Figure 9. DNA damage response after telomestatin treatment of MRC5-V1/YFP-Topo III cells. A, Cells treated for 48 h with 2 mM telomestatin or left untreated were examined for c-H2AX foci (green) that co-localized with TRF1 (red). B, Quantification of the DNA damage foci that co-localized with TRF1. Results are expressed as the percentage relative to c-H2AX foci number and were determined by analysis of more than 50 nuclei. C, Cells treated for 48 h with 2 mM telomestatin or left untreated were examined for c-H2AX foci (red) that co-localized with YFP-Topo III (green). In the magnification at the bottom the co-localization between c-H2AX and Topo III is indicated by arrows. doi:10.1371/journal.pone.0006919.g009 PLoS ONE | www.plosone.org 10 September 2009 | Volume 4 | Issue 9 | e6919