FIG. 6.

ssDNA tails occur in the absence of telomerase, but the telomeres do not elongate. DNA was isolated from strain RWY120 (cdc17-1 tlc1Δ) cells or from strain RWY120 cells carrying a plasmid-borne copy of TLC1 after growth at 23°C (lanes 1 and 5) and after the 23°C culture had been shifted to 30°C for 2 h (lanes 2 and 6), 6 h (lanes 3 and 7), or 24 h (lanes 4 and 8) of growth. (A) Nondenaturing in-gel hybridization with a CA-oligonucleotide probe indicates that the telomeric ssDNA that is present in cdc17-1 cells at 30°C (lanes 2 to 4) is produced even in the absence of telomerase (lanes 6 to 8). (B) Denaturing hybridization with a CA-oligonucleotide probe of the gel in panel A demonstrates that the lanes are approximately evenly loaded. Note that the telomeres are substantially shorter in the cdc17-1 tlc1Δ strain than in the cdc17-1 strain; telomere shortening occurs during the 30 generations of growth at 23°C that is necessary to produce the cdc17-1 tlc1Δ strain (compare telomeric DNA smears [arrow]).