Polycomb group (PcG) protein. Component of the prc2/eed-ezh2 complex, which methylates 'Lys-9' and 'Lys-27' of histone H3, leading to transcriptional repression of the affected target gene (By similarity). Component of the prc2/eed-ezh2 complex (By similarity). Interacts with yy1 (By similarity). Can interact with ezh2, hdac1 and taf9. Maternally and zygotically expressed. Expression declines at the mid-blastula transition. Belongs to the WD repeat ESC family.