Esc4 was identified in an HMR targeted silencing screen. (A) In the presence of both wild-type silencers, HMR-E and HMR-I, the URA3 reporter gene at HMR is completely silenced in a SIR-dependent manner leading to growth in the presence of the drug 5-FOA. (B) When the HMR-E silencer is deleted (and here replaced with a binding site for the Gal4 protein (G)), the HMR locus is no longer silenced and the URA3 reporter gene is expressed. This loss of silencing at hmr::URA3 leads to no growth on 5-FOA media. (C) When the strain in (B) is transformed with a GBD plasmid (GBD-X) capable of causing targeted silencing, this leads to restoration of silencing at hmr::URA3 and growth on 5-FOA. In this way, a GBD hybrid protein library was screened for factors capable of targeted silencing. A GBD-Esc4(1–1070) hybrid was identified.