To examine whether the age-dependent loss of RanBP17 plays an active role in the age-dependent loss of NCC, we generated lentiviruses carrying short hairpin (sh)RNAs against RanBP17 (iR#1 and iR#2; Figure 7A). Efficient knock down of RanBP17 was achieved with both constructs on protein and mRNA levels (Figures 7B and 7C), but cells transduced with iR#2 showed a stronger mRNA decrease and signs of toxicity after 5 days (data not shown). Moderate knock down using iR#1 resulted in a marked increase in GFPnuc/RFPnuc in different cell lines, suggesting a causative role for RanBP17 in the loss of NCC in old cells (Figure 7D). Interestingly, knock down of RanBP17 in young fibroblasts (1 year) changed the expression of 68% of the 78 identified fibroblast aging genes in the same direction, as was observed in progressive aging, further strengthening the idea that RanBP17 plays an upstream role for the cellular aging phenotypes (Figure 7E). Next, since iPSCs from old donors appeared to rejuvenate their transcriptome and restored RanBP17 expression (Figure 7F), we wondered whether iPSC reprogramming might reconstitute proper NCC in old
