Polycomb group (PcG) protein. While PcG proteins are generally required to maintain the transcriptionally repressive state of homeotic genes throughout development, this protein is specifically required during the first 6 hours of embryogenesis to establish the repressed state. Component of the Esc/E(z) complex, which methylates 'Lys-9' and 'Lys-27' residues of histone H3, leading to transcriptional repression of the affected target gene. The Esc/E(z) complex is necessary but not sufficient for the repression of homeotic target genes, suggesting that the recruitment of the distinct PRC1 complex is also required. Component of the Esc/E(z) complex, composed of Caf1-55, esc, E(z), Su(z)12, and possibly pho. The Esc/E(z) complex may also associate with Pcl and HDAC1/Rpd3 during early embryogenesis. 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. Interacts with corto in vitro. Widely expressed. Expressed both maternally and zygotically. Strongly expressed in the oocyte and in early embryos, then decreases at the end of embryogenesis. Weakly expressed in third instar larvae. Transiently required between 2 and 6 hours of embryogenesis to establish PcG silencing and promote viable adults. Belongs to the WD repeat ESC family.