Component of the Clr4 methyltransferase complex (ClrC) which contributes to the establishment of heterochromatin by specifically methylating histone H3 to form H3K9me. ClrC preferentially ubiquitylates H3K14 and ClrC-mediated H3 ubiquitination promotes clr4 methyltransferase activity for the methylation of H3K9. H3K9me represents a specific tag for epigenetic transcriptional repression by recruiting swi6/HP1 to methylated histones which leads to transcriptional silencing within centromeric heterochromatin, telomeric regions and at the silent mating-type loci. Rik1 is involved in the RNAi-mediated targeting of ClrC to heterochromatic repeat elements. Rik1 has also a function in meiotic telomere clustering