Swi6 protein of fission yeast is a functional and structural homolog of HP1 (Heterochromatin Protein 1) of animals and is involved in the formation of heterochromatin structure by binding to centromere, telomere and silent mating-type locus. It is also involved in silencing the genes and sister chromatid cohesion by binding to histone H3 methylated at Lys9 and the cohesin subunit Psc3. It is also involved in the repression of the silent mating-type loci MAT2 and MAT3. It may compact MAT2/3 into a heterochromatin-like conformation which represses the transcription of these silent cassettes.