FIG. 1.

tel1 mutant alleles are similar to tel1Δ in native telomere length maintenance. (A) Kinase activity assay of mutant Tel1p proteins. Tel1p purified from the indicated strains was fractionated by 6% SDS-PAGE and stained by silver staining (bottom panel). The same amounts of Tel1p were tested in a kinase assay using PHAS-I as the substrate (top panel). The position of phosphorylated PHAS-I (pPHAS-I) is indicated by an arrow. Sizes of protein markers (in kDa) are shown on the left. (B) Telomere lengths of strains with chromosomal TEL1 or tel1 alleles expressed from the GAL1 promoter P_GAL1 (lanes 3, 7, 11, 15, 19, and 23, corresponding to strains yYM23, -27, -94, -97, -100, and -103) or from the native TEL1 promoter P_TEL1 (the rest of the samples are strains in which the GAL1 promoter was replaced by the TEL1 promoter, e.g., strains for lanes 4 to 6 were derivatives of yYM23 [lane 3], strains for lanes 8 to 10 were derivatives of yYM27 [lane 7], etc.). Only strains with P_GAL1-TEL1 alleles were grown in galactose-containing medium, and other strains were grown in YPD. (C) Telomere lengths of strains with TEL1 and tel1 alleles combined with mec1Δ and sml1Δ (sml1Δ is not labeled in the figure; parental strains were JHUY817 and yYM242, -244, -246, -248, and -250). Cells were serially streaked on YPD plates, starting from spore colonies every 48 h. Genomic DNA was prepared from streaks 1, 4, 7, 10, and 13 (symbolized by gradient triangles) and analyzed by Southern blotting. Genomic DNA for panel B was prepared from cells after the second restreaking. DNA in panel B was probed with a subtelomeric Y′ probe, and for panel C it was probed with a poly(dA-dC)·(dG-dT) probe. Sizes of DNA markers (in kb) are indicated on the left (B and C).