FIG 4.

A GS-10 linker can alleviate defects in telomere maintenance in endogenously HA-tagged hESCs. (A) Relative expression levels of TERT and OCT4 mRNA in the endogenously epitope-tagged hESCs compared to isogenic wt cells measured by quantitative RT-PCR. Expression of TERT and OCT4 was normalized to GAPDH. HA and HA-GS10 cells whose results are shown in Fig. 2 were targeted independently. (B) Telomeric repeat amplification protocol (TRAP) assay of whole-cell extracts from nonclonal wt, HA, and HA-GS10 hESCs using decreasing amounts of protein (200, 40, and 8 ng). TRAP signals were quantified relative to wt hESCs and are shown at the bottom of the lanes. (C) Telomere restriction fragment assay of the targeted hESCs 42 days after the second targeting.