Component of the kinetochore which plays a role in stabilizing microtubules and so allowing accurate chromosome segregation. Has a role in the RNA interference (RNAi) pathway which is important for heterochromatin formation and accurate chromosome segregation. A member of the RNA-induced transcriptional silencing (RITS) complex which is involved in the biosynthesis of dsRNA from primer siRNAs provided by the RNA- directed RNA polymerase (RDRC) complex. {ECO:0000269|PubMed:10835380; ECO:0000269|PubMed:14704433; ECO:0000269|PubMed:15607976; ECO:0000269|PubMed:9722643}.