FIG. 6.

Effect of TSA on expression levels of transgenes in telomeric clones versus clones with interstitial integration sites containing telomeric repeat sequences. q-RT-PCR using total RNAs isolated from telomeric clones A211, A405, and A353 and interstitial clones I-1, I-2, I-3, and I-7 was used to determine the expression levels of the neo and HSV tk genes relative to that of the mouse GAPDH gene, with (black bars) or without (gray bars) TSA treatment. Note that clone I-2 contains the smallest number of adjacent internal telomeric repeats among the four interstitial clones shown here.