Telomestatin Uncaps Telomeres Figure 4. Effects of telomestatin on Topo III signals and Topo III/TRF2/BLM protein levels in MRC5-V1/YFP-Topo III cells. A, Representative images of untreated MRC5-V1/YFP-Topo III cells and cells treated with 2 mM telomestatin for 48 h; Topo III was detected by fluorescence of YFP-tagged Topo III (green) or by immunofluorescence using D6 antibody (red). Dapi staining of DNA is shown in blue. Telomestatin induced a decrease of Topo III foci number and intensity. B, Cells were treated with telomestatin (0.5 to 5 mM) for 24, 48, or 72 h and Topo III, BLM, TRF2, and actin protein levels were detected by western blot. Telomestatin induced a dose-dependent decrease in Topo III, TRF2, and BLM. C, quantification of the western blot experiment. Result were normalized relative to actin protein levels and expressed relative to control untreated cells, defined as 100%. doi:10.1371/journal.pone.0006919.g004 PLoS ONE | www.plosone.org 5 September 2009 | Volume 4 | Issue 9 | e6919