FIG. 6.

Effect of swd2 mutation on events requiring Set1 activity. (A) H3-K4 dimethylation. An antibody specific to histone H3 dimethylated at H3-K4 was used to detect this species in extracts from swd2 mutants, a strain containing the H3-K4R mutation, the ref2Δ strain, and the respective isogenic wild-type (WT) controls. Cells were grown at 30°C. A nonspecific band detected in the Western blots provides a loading control. (B) H3-K4 trimethylation was detected in the indicated extracts with an antibody specific for this form. (C) Silencing of transcription adjacent to telomeres. URA3 expression was evaluated by spotting serial dilutions of cells onto medium containing 5-FOA or on medium lacking uracil, followed by incubation at 30°C. Impaired growth on 5-FOA medium indicates loss of silencing. (D) Telomere length. Yeast genomic DNA from the indicated strains was digested with XhoI and analyzed by Southern blotting using a portion of the Y′ subtelomeric repeat as the probe. The positions of DNA size markers are indicated on the left.