Mechanisms of Polycomb gene silencing: Knowns and unknowns

Jeffrey A. Simon, Robert E. Kingston

Research output: Contribution to journalReview articlepeer-review

961 Scopus citations


Polycomb proteins form chromatin-modifying complexes that implement transcriptional silencing in higher eukaryotes. Hundreds of genes are silenced by Polycomb proteins, including dozens of genes that encode crucial developmental regulators in organisms ranging from plants to humans. Two main families of complexes, called Polycomb repressive complex 1 (PRC1) and PRC2, are targeted to repressed regions. Recent studies have advanced our understanding of these complexes, including their potential mechanisms of gene silencing, the roles of chromatin modifications, their means of delivery to target genes and the functional distinctions among variant complexes. Emerging concepts include the existence of a Polycomb barrier to transcription elongation and the involvement of non-coding RNAs in the targeting of Polycomb complexes. These findings have an impact on the epigenetic programming of gene expression in many biological systems.

Original languageEnglish (US)
Pages (from-to)697-708
Number of pages12
JournalNature Reviews Molecular Cell Biology
Issue number10
StatePublished - Oct 2009


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