Telomere dynamics in Fancg knock-down primary MEFs with humanlike telomere length (G5 Terc^-/-/Fancg shRNA3 MEFs). (A) Specific Fancg RNA interference was measured by real-time RT-PCR 7 days after infection of P3 wild-type or G5 Terc^-/- MEFs with retroviruses encoding Fancg shRNAs; relative values to a control GFP shRNA are shown. Bars represent average and standard deviation of 2 independent assays. (B) Q-FISH analysis of P3 MEFs 7 days after infection with retroviruses expressing either GFP shRNA or Fancg shRNA3. Most significantly, average telomere length, length distribution, and frequency of signal-free ends were unchanged in G5 Terc^-/-/Fancg shRNA3 MEFs (bottom right panel) compared with their G5 Terc^-/-/GFP shRNA controls (top right panel) despite nearly 90% inhibition of Fancg expression.