FIG. 3.

(A) Effects of deleting the RIF1 gene on growth of Yku⁻ mutants at elevated temperatures. Cells with the indicated genotypes were grown at 23°C to mid-log phase and then diluted into prewarmed medium and regrown for 2.5 or 6 generations at 37°C. Following the growth period in liquid medium, 10-fold serial dilutions of the cells were spotted on SC-Trp and the plates were incubated for 3 days at 37°C. As controls, 10-fold serial dilutions of the cultures prior to the shift to 37°C were also spotted onto SC-Trp and incubated at 23 (top row) or 37°C (second row from top). (B) Telomere lengths in the strains analyzed in panel A. Genomic DNAs from the cultures tested in panel A were digested with XhoI, and the TRFs were detected by standard Southern blotting using a probe that is specific for telomere-proximal Y′ sequences. Lane M, end-labeled 100-bp ladder DNA serving as a size standard. G, generations. (C) In Yku⁻ cells, deletion of the RIF1 gene does not restore a normal terminal DNA structure on telomeres. Aliquots of the genomic DNAs tested in Fig. 3B were analyzed by in-gel hybridization as for Fig. 1B. G-rich overhangs were detected with a CA probe (top). The rehybridization of the gel after denaturation (bottom) indicates that similar amounts of DNA were loaded in each lane.