Figure 4 .

Silencing effect on the expression of EPA1. Schematic representation of the reporter strains. (A) EPA1 was replaced by the URA3 gene and the NE was replaced by the bacterial cat gene and recombined in the chromosome. URA3 reports the activity of the EPA1 promoter. (B) The parental strains NE⁺ and neΔ and the strains carrying null mutations in SIR2–SIR4 (sir2Δ–sir4Δ), (C) HDF1 (yKu70), HDF2 (yKu80), RIF1, and rap1-21 (hdf1Δ, hdf2Δ, and rap1-21), and (D) HST1 and HST2 (hst1Δ and hst2Δ) were grown for 48 hr in YPD. Strains were diluted to OD_600nm 0.5 with distilled water and 10-fold serial dilutions were spotted onto YPD, SC −Ura and SC +5-FOA plates. Plates were incubated at 30°. Ura⁺ cells die on SC +5-FOA plates. Only cells with the URA3 gene transcriptionally repressed can grow on SC +5-FOA. See Materials and Methods.