FIGURE 6.
PinX1-TRF1 interaction is required for TID to inhibit telomere elongation and induce the senescence phenotype in human cells. A, establishment of HT1080 cells stably expressing HA-TID, TIDL291E, or control vector is shown. HT1080 cells were stably transfected with the control vector or a vector expressing HA-TID or its L291E mutant in two independent experiments followed by detecting protein expression using immunoblot with anti-HA antibody. B and C, the L291E mutation abolishes the ability of TID to induce telomere shortening in human cells. Stable cells were maintained continuously in culture and harvested at various PDs as indicated, and genomic DNA was isolated and digested with HinfI and RsaI followed by in-gel hybridization with a TTAGGG repeat probe (B). Before hybridization, gels were stained with ethidium bromide to check loading of genomic DNA (C). D–F, the L291E mutation abolishes the ability of TID to induce the senescence phenotype in human cells. HT1080 cell lines stably transfected with the control vector (D) or expressing similar levels of TID (E) and TIDL291E (F) were fixed at 16 PDs and then subjected to senescence-associated β-galactosidase staining followed by microscopy.