Non-coding RNAs in polycomb/trithorax regulation.

The Polycomb (PcG) and Trithorax (TrxG) proteins are epigenetic regulators that maintain correct expression patterns of several hundred developmentally important genes by binding to DNA regulatory elements called Polycomb/Trithorax Response Elements (PRE/TREs). Many PRE/TREs are transcribed into long non-coding RNAs. Furthermore, many PcG and TrxG proteins bind to RNA, and recent evidence suggests that these RNA interactions are essential for targeting both groups of proteins to specific sites, and modulating their effects on gene expression. We discuss current evidence for the molecular mechanisms by which non-coding RNAs may recruit PcG and TrxG proteins, switch gene expression states, and maintain epigenetic memory.