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Fig. 5 | Epigenetics & Chromatin

Fig. 5

From: RNAi-dependent heterochromatin assembly in fission yeast Schizosaccharomyces pombe requires heat-shock molecular chaperones Hsp90 and Mas5

Fig. 5

Model. Formation of the siRNA-containing complexes ARC and RITS are key steps in the assembly of RNAi-dependent heterochromatin at the pericentromere. In ARC and RITS complexes, the Argonaute protein Ago1 binds double-stranded and single-stranded siRNA, respectively. The subunits of the non-chromatin-associated ARC complex are responsible for the loading of siRNA onto Ago1, which is then incorporated into the RITS complex. RITS acts in the center of the self-enforcing loop of RNAi-dependent heterochromatin assembly. RITS recruits the RNA-dependent RNA polymerase complex (RDRC) for siRNA generation, while also recruiting (via Stc1) the Clr4-containing methyltransferase complex that methylates H3K9. The generation of siRNA and loading of siRNA onto Ago1 in vivo require Hsp90 and Mas5. Mas5 also maintains the protein level of the RITS subunit Tas3. Thus, Hsp90 and Mas5 are required for RNAi-dependent heterochromatin assembly

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