Has a role in the RNA interference (RNAi) pathway which is important for heterochromatin formation, accurate chromosome segregation, centromere cohesion and telomere function during mitosis and meiosis. Required for both post-transcriptional and transcriptional gene silencing. Required for silencing at the centromeres and for initiation of transcriptionally silent heterochromatin at the mating type locus. Promotes histone H3 'Lys-10' methylation necessary for centromere function. Required for recruitment of swi6 and cohesin to an ectopic dg repeat. A member of the RNA-directed RNA polymerase complex (RDRC) which is involved in the generation of small interfering RNAs (siRNAs) and mediates their association with the RNA-induced transcriptional silencing (RITS) complex. RITS acts as a priming complex for dsRNA synthesis at the site of non-coding centromeric RNA. Its RNA-dependent RNA polymerase activity is critical in siRNA production necessary for heterochromatin formation. a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) Cid12, hrr1 and rdp1 interact forming the RNA-directed RNA polymerase complex (RDRC). The RDRC complex interacts with the RITS complex via interaction between ago1 and hrr1. Clr4 has a role in mediating this interaction. Associates with telomeric and mating-type region heterochromatin. Belongs to the RdRP family.