The Paramecium PRC2 complex physically interacts with the RNAi pathway

Le résumé fourni par la source

In addition to its role in the transcriptional repression of protein-coding genes, the Polycomb Repressive Complex 2 (PRC2) and its H3K27me3 activity silence transposable elements in diverse eukaryotes. How PRC2 is tethered to transposable elements remains mysterious. To address this question, we performed tandem affinity purification combined with mass spectrometry and identified the proteins that physically interact with the Paramecium Enhancer-of-zeste Ezl1 enzyme, which deposits H3K9me3 and H3K27me3 at transposable elements. We showed that the Paramecium PRC2-Ezl1 core complex is formed around four subunits, required in vivo for catalytic activity. PRC2 cofactors were identified, among which the RNAi effector Ptiwi09, and shown necessary to target H3K9me3 and H3K27me3 at transposable elements. The physical interaction between the PRC2-Ezl1 complex and the RNAi pathway was shown to be mediated by a RING finger protein, unraveling an analogous mechanism to that described for the recruitment of H3K9 methylation SU(VAR)3-9 enzymes.

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