Antagonizing Polycomb group-mediated gene repression by chromatin remodelers.

Cellular identity is maintained by epigenetic processes that prevent changes of cell-type specific transcriptional programs. Polycomb group (PcG) proteins are evolutionary conserved key players of cellular identity that repress central developmental regulators by modifying chromatin structure. PcG-mediated repression is antagonized by trithorax group (trxG) proteins that prevent inappropriate repression by PcG proteins. The molecular basis for this antagonistic activity is unclear. So far, only few chromatin regulatory proteins have been associated with trxG function in Arabidopsis. Recent work revealed that ATP-dependent chromatin remodeling factors of the Chromodomain-Helicase-DNA-binding (CHD) subfamily have trxG-like functions in Arabidopsis. Here we will discuss the implications of these findings that point towards an evolutionary conservation of PcG/trxG mediated gene regulation in higher eukaryotes.