 Although this mark represses the lineage control genes, it does keep them ready for activation upon differentiation.When the cell receives the signal to differentiate to a specific type of cell, H3K27me3 will be removed from the genes needed for differentiation, while H3K27me3 maintains repression of developmental control genes that are unnecessary for the chosen lineage.The developmentally regulated process of resolving bivalent chromatin is aided by the activity of ATP-chromatin remodelers such as SWI/SNF, which hydrolyze ATP to evict Polycomb-group proteins from bivalent chromatin.