An RNA degradation complex required for silencing of Polycomb target genes

Polycomb Repressive Complex (PRC) 1 and 2 are histone-modifying and chromatin-binding complexes that are required for silencing of developmental regulatory genes and genes that control cellular proliferation. Their gene silencing functions are thought to involve chromatin compaction and condensate formation but whether other mechanisms contribute to silencing is unknown. Here we show that the rixosome, a conserved RNA degradation complex with roles in ribosomal RNA processing and heterochromatic RNA degradation in fission yeast, associates with human PRC complexes, is recruited to promoters of Polycomb target genes in differentiated cell lines and embryonic stem cells, and is required for efficient silencing of Polycomb target genes. These findings reveal an unanticipated role for RNA degradation in Polycomb-mediated silencing.