Position-dependent effects of CTR9 deletion on transcription and silencing. (A) The wild-type strains JHY49 and JHY25 each contain a single copy of URA3 integrated 11.5 Kb and 55 Kb, respectively, downstream of the natural left telomere of chromosome XV, as diagrammed above. Into these strains were introduced npt1Δ (HM193, HM190), bna1Δ (HM192, HM189) and ctr9Δ (HM191, HM188) deletions. Cells were diluted serially 10-fold and plated on SC, 5FOA or SC -ura as indicated. (B) The wild-type YCB647 strain carries a single copy of URA3 integrated into the left telomere of chromosome VII, as diagrammed above. Into this strain, set1Δ (HM206), set2Δ (HM207), ctr9Δ (HM180) or paf1Δ (HM205) deletions were introduced. Cells were diluted serially 5-fold and plated on SC, 5FOA, or SC -ura as indicated. (C) The wild-type YCB761 strain contains a single copy of ADE2 integrated into the right telomere of chromosome V as shown above. This and derivatives carrying npt1Δ (JS692) or ctr9Δ (HM182) deletions were plated on SC containing limiting adenine.