Recognizes and binds histone H3 tails methylated at 'Lys-9', leading to epigenetic repression. Involved in the repression of the silent mating-type loci MAT2 and MAT3. May compact MAT2/3 into a heterochromatin-like conformation which represses the transcription of these silent cassettes. Interacts with histone H3 methylated at 'Lys-9'. Interacts with the cohesin subunit psc3 and with hrk1.