Involved in the establishment; but not the maintenance; of heterochromatic silencing at the cryptic mating-type loci HMR and HML. Is recruited by interacting with the ORC1 subunit of the origin recognition complex (ORC); which binds to HML-I or HMR-E silencers; DNA elements that direct the formation of silent chromatin at the mating-type loci. Establishes transcriptional silencing by recruiting the three other SIR proteins; SIR2; SIR3; and SIR4; that function directly in silenced chromatin and establish repression. Also found in centromeric chromatin. Binds to and helps retain CAC1; a subunit of chromatin assembly factor I (CAF-I) at centromeric loci independent on the other SIR proteins. {ECO:0000269|PubMed:12134062; ECO:0000269|PubMed:8221892; ECO:0000269|PubMed:8622770}.