Polycomb group (PcG) protein. In contrast to other PcG protein, it is specifically required during the first 6 hours of embryogenesis to establish PcG silencing. PcG proteins act by forming multiprotein complexes, which are required to maintain the transcriptionally repressive state of homeotic genes throughout development. PcG proteins are not required to initiate repression, but to maintain it during later stages of development. They probably act via a methylation of histones, rendering chromatin heritably changed in its expressibility. Component of the Esc/E(z) complex, which methylates 'Lys-9' and 'Lys-27' residues of histone H3. The Esc/E(z) complex is necessary but not sufficient to recruit a functional PcG repressive complex that represses target genes, suggesting that the recruitment of the distinct PRC1 complex is also required to allow a subsequent repression (By similarity). Component of the Esc/E(z) complex, composed of Esc, E(z), Su(z)12, Rpd3, Caf1 and probably Pho. This complex is distinct from the PRC1 complex, which contains many other PcG proteins like Pc, Ph, Psc, Su(z)2. The two complexes however cooperate and interact together during the first 3 hours of development to establish PcG silencing (By similarity). Phosphorylated. Belongs to the WD repeat ESC family.