Figure 7.

Model for RNAi-independent functions of Ago1 and Dcr1. The right side of the model depicts the classical RNAi pathway in which Rdp1 is required for production/amplification of centromere-derived double-strand transcripts (cenH) that serve as substrates for Dcr1. The resulting siRNAs are incorporated into Ago1-containing RISCs that facilitate heterochromatin formation, an event that is required for attachment of mitotic spindles to kinetochores and subsequent orderly chromosome segregation. The left side of the model depicts a pathway in which Dcr1 and Ago1 in response to genotoxic insults such as DNA damage or HU, mediate downstream events that lead to inhibitory phosphorylation of Cdc2. This process is proposed to be independent of siRNAs and Rdp1.