Polycomb group (PcG) protein. Catalytic subunit of some PcG multiprotein complex, which methylates 'Lys-27' of histone H3, leading to transcriptional repression of the affected target genes. Required to prevent the proliferation of the central cell of the female gametophyte by repressing target genes before fertilization. After fertilization, it probably also regulates the embryo and endosperm proliferation and anteroposterior organization during seed development. 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. Interacts with the promoter and repress the transcription of genes such as PHE1 and PHE2, that are paternally active and maternally silenced genes. L-lysyl(27)-[histone H3] + 3 S-adenosyl-L-methionine = 3 H(+) + N(6),N(6),N(6)-trimethyl-L-lysyl(27)-[histone H3] + 3 S-adenosyl-L-homocysteine Interacts directly with FIE via its N-terminal domain. These two proteins are probably indirectly associated with FIS2. In plants, PcG complexes are probably composed of a member of the EZ family (CLF or MEA), FIE, and a member of the VEFS family (FIS2, VRN2 or EMF2). Interacts with TAF13. Excluded from the nucleolus. Expressed in unpollinated siliques that contain maturing gametophytes. Not expressed at early stages of floral development during early megagametogenesis. Expressed both maternally and zygotically. Expressed in both egg and central cell before fertilization. After fertilization, it is expressed in the embryo and endosperm, then decreases during seed maturation. Maternal MEA allele is activated by DME but repressed by MET1 in the central cell of the female gametophyte, the progenitor of the endosperm. The MEA locus is imprinted. Maternal inherited gene is expressed in the ovule (the egg and the central cell), while the paternal inherited gene is silenced in the pollen. After fertilization, only the maternal inherited allele is expressed. The paternal repression is dependent on DDM1 protein, which may methylate the paternal locus, while the maternal inherited allele is allowed by the DME protein, which may antagonize or suppress DDM1 dependent methylation, and activates its transcription. Belongs to the class V-like SAM-binding methyltransferase superfamily. Histone-lysine methyltransferase family. EZ subfamily.