Practice question

At fission yeast pericentromeres RITS complex links RNA recognition to chromatin modification co-transcriptionally. RITS contains Ago1 loaded with Dicer-produced centromeric siRNAs, chromodomain Chp1 binding H3K9 methylation, and Tas3 bridging to CLRC. When Pol II transcribes repeats producing nascent RNA, siRNA-nascent pairing tethers RITS recruiting CLRC containing Clr4 methyltransferase. H3K9 methylation creates binding sites for Swi6 HP1 and further Chp1 establishing positive feedback reinforcing silencing. RITS thus translates RNAi recognition into heterochromatin assembly ensuring transcriptional gene silencing and epigenetic inheritance of centromeric domains required for kinetochore assembly and chromosome segregation fidelity.