Figure 2.
Model for RNAi-mediated heterochromatin formation in S. pombe. siRNA guided RITS complex targets the centromeric nascent transcript synthesized by RNA polymerase II during the S phase of the cell cycle. RITS associates with RDRC complex, where the RdRP activity of the RDRC complex generates more dsRNA. Dcr1 processes the dsRNA into siRNA, feeding into the loop. CLRC complex associates with the RITS complex, which comes into close proximity with the chromatin. Clr4 methylates H3K9 and allows Swi6 (HP1 homolog) to dock at the modified chromatin, thereby forming heterochromatin.