PRC2 initiates gene repression by tri-methylating lysine 27 on histone H3 (H3K27me3). This mark is recognized by PRC1, which then ubiquitinates histone H2A at lysine 119 (H2AK119ub1), further consolidating gene repression. The interplay between these complexes ensures that certain genes remain in an inactive state, which is essential for processes like cell differentiation and development.
