Editing Cellular differentiation (section)

====Trithorax group proteins (TrxG)====
Alternately, upon receiving differentiation signals, PcG proteins are recruited to promoters of pluripotency transcription factors. PcG-deficient ES cells can begin differentiation but cannot maintain the differentiated phenotype.<ref name= "Christophersen"/> Simultaneously, differentiation and development-promoting genes are activated by Trithorax group (TrxG) chromatin regulators and lose their repression.<ref name= "Christophersen"/><ref name = "Guenther"/> TrxG proteins are recruited at regions of high transcriptional activity, where they catalyze the trimethylation of histone H3 lysine 4 ([[H3K4me3]]) and promote gene activation through histone acetylation.<ref name = "Guenther"/> PcG and TrxG complexes engage in direct competition and are thought to be functionally antagonistic, creating at differentiation and development-promoting loci what is termed a "bivalent domain" and rendering these genes sensitive to rapid induction or repression.<ref name = "Meissner">{{cite journal | vauthors = Meissner A | title = Epigenetic modifications in pluripotent and differentiated cells | journal = Nature Biotechnology | volume = 28 | issue = 10 | pages = 1079–1088 | date = October 2010 | pmid = 20944600 | doi = 10.1038/nbt.1684 | s2cid = 205274850 }}</ref>