FIG. 7.

Telomere length of tsFT20 cells that had been transiently cultured at semipermissive temperature. A. Protocol of the experiment. tsFT20 cells that had been cultured at 33°C or 38°C for 4 weeks were prepared (week zero). The 38°C cultures were divided into two: one was kept at 38°C, while the other was shifted to 33°C and cultured for an additional 12 weeks. The cells were harvested at the indicated time points and analyzed for telomere length as for Fig. 2. B. Telomere lengths of cells shown in panel A. C. G-tail signals of cells indicated in panel A. DNA samples were treated [Exo I (+)] or not treated [Exo I (-)] with Exo I prior to HinfI digestion. After in-gel hybridization and autoradiography (nondenatured), the gel was denatured and reprobed with the same telomeric oligonucleotide probe (denatured). D. The G-tail signal intensities obtained in panel C were quantitated and normalized to the signal intensity of the ∼4.0-kb internal telomeric band detected under denatured conditions. The value obtained for cells grown stably at 33°C is set at 1.0 (panel C, lane 1). Similar results were obtained from four independent experiments.