PRC2 Complex 6C24

Transcriptionally repressive histone H3K27 methylation by PRC2 (Polycomb repressive complex 2) is essential for cellular differentiation and development. Here we report cryo-EM structures of human PRC2 in two distinct, active states, while in complex with its cofactors JARID2 and AEBP2. Both cofactors mimic the binding of histone H3 tails. JARID2, methylated by PRC2, mimics a methylated H3 tail to stimulate PRC2 activity, while AEBP2 interacts with the RBAP48 subunit mimicking an unmodified H3 tail. SUZ12 interacts with all other subunits within the assembly and thus contributes to the stability of the complex. Our analysis defines the complete architecture of a functionally relevant PRC2 and provides a structural framework to understand its regulation by cofactors, histone tails and RNA