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. 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 (By similarity). Involved in histone methylation and transcription regulation (Probable). 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 Component of the polycomb repressive complex 2 (PRC2), which methylates 'Lys-27' residues of histone H3 (H3K27me3), leading to transcriptional repression of the affected target gene. Expressed in roots, leaves, shoots, rachis, anthers and embryos. Expressed in emerging young seedlings from 3 to 4 days after seed imbibition. Belongs to the class V-like SAM-binding methyltransferase superfamily. Histone-lysine methyltransferase family. EZ subfamily.