Figure 1. Schematic of Polycomb and Trithorax Related Proteins at Promoters of Repressed and Active Genes.
Repressed genes are bound by Polycomb group proteins (PcG) whereas Trithorax-related proteins (TrxG) localize to actively transcribed genes. COMPASS (complex of proteins associated with Set1) opposes PcG activity to activate transcription. ATP-dependent chromatin remodelers (CHD, ISWI, INO80, and SWI/SNF) regulate DNA accessibility, which influences gene repression and activation during embryonic development.